Books on quantum physics and associated philosophy
Chris Vinall
This message is crossposted to alt.philosophy, sci.physics and
sci.physics.research since to my surprise there are no groups in either
alt.philosophy.* or sci.physics.* that seem directly appropriate (the lack
of sci.physics.quantum seems especially strange). Apologies in advance if
this is going to inappropriate groups.
I have a basic grasp of the Copenhagen interpretation of quantum mechanics
and am looking to buy books which deal with the philosophical implications
of the theory, especially as it relates to the measurement problem and the
role of consciousness in the theory. I am interested in the parallels that
appear with Eastern mysticism and in theories like Wheeler's that implicate
consciousness in the basic structure of the universe, but would be equally
interested in books that argue against these - I am looking simply for
informed discussion of the subject. If my knowledge of the physics is
expanded at the same time, so much the better. I want the book to have a
sound scientific basis - a quick flick through "Quantum Self" by Danar
Zohar, for example, revealed a section on "Quantum relationships" which
explored whether people's "wave functions were in harmony". I want to avoid
this sort of rubbish but would like the book to be readable and not get
bogged down in maths. Finally, I am vehemently opposed to the "many-worlds"
interpretation so I would like the book to not advocate that theory too
enthusiastically.
A quick scan of the shelves at a local bookshop revealed the following
likely-looking titles, which might give an idea of the kind of thing I'm
after:
Bohm, D "Wholeness and the Implicate Order"
Bohm, D & Hiley, BJ "The Undivided Universe"
Capra, F "The Tao of Physics" (I have heard accusations against this book of
being a bit lacking in substance)
Gribbin, J "In Search of Schroedinger's Cat" and "Schroedinger's Kittens"
Herbert, N "Quantum Reality"
Nadeau & Kafatos "The Non-Local Universe"
Penrose, R "The Large, The Small and the Human Mind" & "Shadows of the Mind"
Wilber "Quantum Questions"
Zokav, Gary "The Dancing Wu Li Masters"
Goswami, Maggie "The Self-Aware Universe: How Consciousness Creates the
Material World"
If you have a favourite book that isnt included in the above, by all means
suggest it anyway. A brief rundown on the contents of any suggestion would
be much appreciated.
Thanks in advance!
Chris Vinall
Arkadiusz Jadczyk
>If you have a favourite book that isnt included in the above, by all means
>suggest it anyway. A brief rundown on the contents of any suggestion would
>be much appreciated.
Mathematische Grundlagen der Quantnmechanik
by Johann V. Neumann
(or English translation
Speakable and unspeakable in quantum mechanics
By J.S. Bell
Geons, Black Holes and Quantum Foam
by J.A. Wheeler
The Philosopher's Stone
by F. David Peat
What is life?
by Erwin Schroedinger
ark
--
Arkadiusz Jadczyk
http://www.cassiopaea.org/quantum_future/homepage.htm
--
Richard
> Herbert, N "Quantum Reality"
This one specifically addresses all of the various schools of thought
that emerged from quantum theory, and does so in a fairly unbiased, and
tidy fashion. Check the Amazon synopsis and reviews on this book, and
the others on your list as well.
>
> If you have a favourite book that isnt included in the above, by all means
> suggest it anyway. A brief rundown on the contents of any suggestion would
> be much appreciated.
>
> Thanks in advance!
>
> Chris Vinall
--
Richard
http://www.cswnet.com/~rper
--The dissenter is every human being at those moments of his life when
he resigns momentarily from the herd and thinks for himself.
--Archibald MacLeish
Robert Kolker
Chris Vinall wrote:
> If you have a favourite book that isnt included in the above, by all means
> suggest it anyway. A brief rundown on the contents of any suggestion would
> be much appreciated.
You are reading popularizations with a lot of woo woo new age horseshit.
Why not read some -physics-. How about volume 3 of the Feynman Lectures.
Bob Kolker
P.S. If you come accross any books by Frad Alan Wolfe, consign them to
the flames.
Leonardo Dasso
"Chris Vinall" <cvi...@REMOVEihugTHIS.com.au> wrote in message
news:arhmlg$3e9$1...@lust.ihug.co.nz...
[Sci.physics.research moderator's note: Quoted text deleted. Please
edit quoted text judiciously, lest I do it injudiciously, as I've
done here. -TB]
Check Prof Victor Stenger's book "The Unconscious Quantum: Metaphysics
in Modern Physics and Cosmology"
You can find comments and excerpts from the book in
http://spot.colorado.edu/~vstenger/meta.html
regards
leo
Danny Ross Lunsford
> Mathematische Grundlagen der Quantnmechanik
> by Johann V. Neumann
> (or English translation
>
> Speakable and unspeakable in quantum mechanics
> By J.S. Bell
>
> Geons, Black Holes and Quantum Foam
> by J.A. Wheeler
>
> The Philosopher's Stone
> by F. David Peat
>
> What is life?
> by Erwin Schroedinger
Neat! "Space Time Structure" by Schroedinger.
You left out "Principles of Quantum Mechanics" by P.A.M. Dirac.
-drl
Toby Bartels
>Finally, I am vehemently opposed to the "many-worlds"
>interpretation so I would like the book to not advocate that theory too
>enthusiastically.
A warning about "many worlds" theories.
The term "many worlds" is often used for any idea
stemming from Everett's 1950s PhD thesis.
But this term was invented (I think) by Deutsch,
and there are a lot of people that agree with Everett
but think that Deutsch's interpretation of Everett's interpetation
is still completely wrong. So don't be prejudiced,
especially if something is referred to as "many worlds"
by its opponents but not by its supporters.
>Bohm, D "Wholeness and the Implicate Order"
>Bohm, D & Hiley, BJ "The Undivided Universe"
Bohm & Hiley is the standard reference for Bohm's theory
which, while unpopular, is an important idea.
>Capra, F "The Tao of Physics" (I have heard accusations against this book of
>being a bit lacking in substance)
This is a classic for relationships to Eastern mysticism.
I'd argue that anything advocating such a relationship
is a bit lacking in substance, on the grounds that
the relationship in question itself lacks substance.
But I don't think that you can do better than this book
if you want something arguing for that relationship.
>If you have a favourite book that isnt included in the above, by all means
>suggest it anyway. A brief rundown on the contents of any suggestion would
>be much appreciated.
Omnes, The Interpretation of Quantum Mechanics
-- Toby
john bailey
<cvi...@REMOVEihugTHIS.com.au> wrote:
>I have a basic grasp of the Copenhagen interpretation of quantum mechanics
>and am looking to buy books which deal with the philosophical implications
>of the theory, especially as it relates to the measurement problem and the
>role of consciousness in the theory. I am interested in the parallels that
>appear with Eastern mysticism and in theories like Wheeler's that implicate
>consciousness in the basic structure of the universe, but would be equally
>interested in books that argue against these - I am looking simply for
>informed discussion of the subject.
There are five widely discussed interpretations of quantum physics--1)
the Copenhagen interpretation, 2) the many-worlds interpretation, 3)
quantum logic, 4) coherent histories and 5) information physics.
The Copenhagen interpretation: *if the math agrees with the outcomes,
don't ask questions--shit happens*
The many-worlds interpretation requires a large leap of acceptance--
that there are almost uncountably many parallel universes which
continue to spring up at every quantum event.
Quantum logic says that boolean logic does not apply to all physical
situations. It provides an abstract reconstruction of the laws of
reason which proports to end with a logical explaination of the weird
laws of quantum mechanics.
The information physics answer seems to be incomplete but it explains
quantum effects in general as the behavior of systems which are
inherently limited in the amount of information they can yield.
Consistent histories eliminates paradoxes and odd behavior by
rigorously constraining the conditions under which math applies to an
experiment.
Reasonably useful papers on some of these interpretations can be
obtained from the Los Alamos National Library reprint archive.
(The format for getting an abstract is:
http://xyz.lanl.gov/abs/gr-qc/9903084)
zeh2.pdf quant-ph0204088 The Wave Function: It or Bit Fundamentals of
Quantum Information Theory
plenio.pdf quant-ph0103108 Solid, comprehensive, insightful treatment
of information physics. Extensive treatment of Landauer's
principle, 2nd Law of Thermodynamics and entropy--Shannon's and Von
Neumann's.
hawking.pdf hep- th/ 9409195 Three lectures: quantum gravity and
cosmology. No boundaries, entropy, and the consequences of
thinking about past, present and future.
t'hooft.pdf gr-qc/9903084 Quantum Gravity as a dissapative
deterministic system Gerard t' Hooft Presents an alternative
unification approach. Page 14 discusses its departure from the Many
Worlds interpretation.
equilbrm.pdf Randomness As An Equilibrium. Potential And Probability
Density Marian Grendar, Jr. and Marian Grendar Ties
randomness, Fisher information, entropy together in a paradigm of
gaseous diffusion. http://www.jhuapl.edu/maxent2001/028Grendar.pdf
nt_cnsts.pdf astro- ph/ 9909295 Why the Universe is just so Craig
Hogan Twenty parameters are needed for the standard model.
Of these, some are given by symmetry and others are the result of
random outcome of an underfined selection process
Catchia.pdf gr-qc10109068 Entropic Dynamics Deriving physics from
Baysian inference and max entropy.
decohernc.pdf quant-ph9908008 Elements of enviormental Decoherence
Decoherence is very rapid. Zeh is okay.
>If you have a favourite book that isnt included in the above, by all means
>suggest it anyway. A brief rundown on the contents of any suggestion would
>be much appreciated.
The Structure and Interpretation of Quantum Mechanics by Hughes
Contains the best but still incomprehensible discussion of quantum
logic as a foundation.
Feynman and Computation anthology
Several incomplete fragments of explainations of information physics
Quantum Theory by Bohm
Bohm's basic text, written prior to his developing his holistic
hidden variable theory interpretation.
Mathematics of Classical and Quantum Physics Byron and Fuller
John Bailey
http://home.rochester.rr.com/jbxroads/mailto.html
Charles Francis
In article <arhmlg$3e9$1...@lust.ihug.co.nz>, Chris Vinall
<cvi...@REMOVEihugTHIS.com.au> writes
>Bohm, D "Wholeness and the Implicate Order"
>Bohm, D & Hiley, BJ "The Undivided Universe"
I've not read Bohm, and am not keen on Bohmian mechanics, but I would
expect these to be intelligent
>Capra, F "The Tao of Physics" (I have heard accusations against this book of
>being a bit lacking in substance)
A bit!!! Capra's argument goes like this. "here is a quote from a 20th
century physicist, here is a quote translated from a tibetan monk from
the 10th century. The translation uses a word of three or more
syllables, and the physicist uses exactly the same word! therefore
modern physicists and ancient Eastern mystics are saying exactly the
same thing".
>Gribbin, J "In Search of Schroedinger's Cat" and "Schroedinger's Kittens"
Gribbin does a workmanlike job of explaining things to non-physicists.
>Penrose, R "The Large, The Small and the Human Mind" & "Shadows of the Mind"
Presumably also The Emperor's New Mind.
>Zokav, Gary "The Dancing Wu Li Masters"
Fritjof Capra got rich on it, so why cannot Gary Zukav? If possible this
book is even worse than the Tao of Physics.
Although they do not discuss consciousness, Don't omit important books
on the philosophy of qm, notably Heisenberg, Physics and Philosophy, and
Feynman, The character of physical law.
Regards
--
Charles Francis
Gjergj Kastrioti
> You are reading popularizations with a lot of woo woo new age horseshit.
> Why not read some -physics-. How about volume 3 of the Feynman Lectures.
>
> Bob Kolker
check heisenberg's books on philosophy
http://www.amazon.com/exec/obidos/search-handle-form/103-8792260-8019862
John Baez
In article <arhmlg$3e9$1...@lust.ihug.co.nz>,
Chris Vinall <cvi...@REMOVEihugTHIS.com.au> wrote:
>I am interested in the parallels that
>appear with Eastern mysticism and in theories like Wheeler's that implicate
>consciousness in the basic structure of the universe, but would be equally
>interested in books that argue against these - I am looking simply for
>informed discussion of the subject. If my knowledge of the physics is
>expanded at the same time, so much the better. I want the book to have a
>sound scientific basis - a quick flick through "Quantum Self" by Danar
>Zohar, for example, revealed a section on "Quantum relationships" which
>explored whether people's "wave functions were in harmony". I want to avoid
>this sort of rubbish [...]
So I guess you won't be wanting my book "Quantum Seduction", which
features classic pickup lines like:
"Wanna tunnel over to my pad and collapse into an entangled state?"
and a complete guide to which interpretations of quantum
mechanics attract which types of women.
> [...] but would like the book to be readable and not get
> bogged down in maths.
Oh, so you won't be wanting my "Introduction to Algebraic
and Constructive Quantum Field Theory", either. Shucks.
>Finally, I am vehemently opposed to the "many-worlds"
>interpretation so I would like the book to not advocate that theory
>too enthusiastically.
>A quick scan of the shelves at a local bookshop revealed the following
>likely-looking titles, which might give an idea of the kind of thing I'm
>after:
>
>Bohm, D "Wholeness and the Implicate Order"
>Bohm, D & Hiley, BJ "The Undivided Universe"
I dislike Bohm's approach to quantum mechanics, but he
knows his stuff, and he invented a strange new way of
thinking about it that's notoriously hard to shoot down.
>Capra, F "The Tao of Physics" (I have heard accusations against this
>book of being a bit lacking in substance)
I loved this book in high school, but then I learned
more physics and more philosophy, and decided it was a bit
silly. One annoying thing about this book is that he lumps
together all sorts of Asian philosophies as if they were one
big undifferentiated grab-bag just waiting to be ransacked
for quotes - a little Zen here, a little Taoism there, etc..
If you can imagine someone treating "Western Philosophy" as
a single entity and indiscriminately quoting Heraclitus,
Hegel and Nietzsche to prove that "modern physics is a lot
like Western Philosophy", maybe you'll get what I mean.
>Gribbin, J "In Search of Schroedinger's Cat" and "Schroedinger's Kittens"
>Herbert, N "Quantum Reality"
These are the sort of books I prefer to read while sipping coffee at
Barnes and Noble, so I don't have to actually pay for them. Does
your bookstore have a cafe in it? It might come in handy.
>Nadeau & Kafatos "The Non-Local Universe"
Never heard of it.
>Penrose, R "The Large, The Small and the Human Mind" &
>"Shadows of the Mind"
Penrose is a real physicist, who has done some wonderful
things in general relativity. He thinks quantum mechanics
in its current formulation is fatally flawed (for reasons
I don't sympathize with). These days he spends a lot of
energy trying to invent a new version of quantum mechanics in
which gravitational interactions collapse the wavefunction.
He also has some ideas on how the quantum mechanical behavior
of microtubules in the brain might be important in consciousness;
these seem plain wrong.
>Wilber "Quantum Questions"
Don't know it.
>Zukav, Gary "The Dancing Wu Li Masters"
This is sort of like a bargain-basement version of "The Tao
of Physics".
>Goswami, Maggie "The Self-Aware Universe: How Consciousness Creates the
>Material World"
I don't know this one.
>If you have a favourite book that isnt included in the above, by all means
>suggest it anyway. A brief rundown on the contents of any suggestion would
>be much appreciated.
I really urge that you learn quantum mechanics. It's a
wonderful subject, full of surprises, and one of the great
things about it is that you can actually use it to understand
the behavior of light, atoms, molecules, transistors, etc..
None of the books on your list which I've actually read will
teach you quantum mechanics. An ounce of actual knowledge is
worth a ton of second-hand opinions.
It can't hurt to start with
Richard Feynman, QED: the Strange Theory of Light and Matter,
Princeton University Press, Princeton, 1985.
It's a fun book without too much math, and Feynman is a
real character. Eventually however you should try something
more substantial - maybe someone out there can suggest some
good introductions to quantum mechanics.
It's also good to read histories of physics. Here are some
of my favorites:
From Falling Bodies to Radio Waves: Classical Physicists and Their
Discoveries, W. H. Freeman, New York, 1984.
Emilio Segre,
From X-Rays to Quarks: Modern Physicists and Their Discoveries,
W. H. Freeman, San Francisco, 1980.
Abraham Pais,
Inward Bound: of Matter and Forces in the Physical World,
Clarendon Press, New York, 1986.
Robert P. Crease and Charles C. Mann,
The Second Creation: Makers of the Revolution in Twentieth-Century
Physics, MacMillan, New York,
1986.
Finally, if you want to read about so-called "Eastern mysticism",
I urge that you read the Tao Te Ching, the Chuang-Tze, and
stuff by Daisetz Suzuki. It'll knock your socks off.
Why settle for second-hand accounts by white boys when
you can get the real thing? :-)
Anna&Will
"Chris Vinall" <cvi...@REMOVEihugTHIS.com.au> wrote in message news:<arhmlg$3e9$1...@lust.ihug.co.nz>...
quoted text you include or the moderators will do it for you. -- KS]
Thanks for posting the question. I have the same question. Anyone
read "Quantum Philosophy" by Roland Omnes? If you have, what was
like? Thanks.
Peter Woit
John Baez wrote:
>In article <arhmlg$3e9$1...@lust.ihug.co.nz>,
>Chris Vinall <cvi...@REMOVEihugTHIS.com.au> wrote:
>
>
>
>>Capra, F "The Tao of Physics" (I have heard accusations against this
>>book of being a bit lacking in substance)
>>
>>
>
>I loved this book in high school, but then I learned
>more physics and more philosophy, and decided it was a bit
>silly. One annoying thing about this book is that he lumps
>together all sorts of Asian philosophies as if they were one
>big undifferentiated grab-bag just waiting to be ransacked
>for quotes - a little Zen here, a little Taoism there, etc..
>If you can imagine someone treating "Western Philosophy" as
>a single entity and indiscriminately quoting Heraclitus,
>Hegel and Nietzsche to prove that "modern physics is a lot
>like Western Philosophy", maybe you'll get what I mean.
>
>
Another important thing to point out is that no matter what you think of
Capra's Eastern philosophy, his physics is completely discredited garbage.
The "bootstrap philosophy" which he explains in detail and which he
claims is so in tune with the East is just simply wrong. You simply can't
derive the strong interaction S-matrix from the hypothesis of analyticity
or by thinking of all hadrons as bound states of each other. The fact that
he keeps putting out new editions of this book, adding new afterwords
about how Geoff Chew is the greatest physicist of the twentieth century,
quarks don't make any sense and the bootstrap is making great progress is
bald-faced charlatanry. As a physicist, the man is a complete crank
and the fact that his book still sells well in every Barnes and Noble
in the land is a disgrace.
>
>Finally, if you want to read about so-called "Eastern mysticism",
>I urge that you read the Tao Te Ching, the Chuang-Tze, and
>stuff by Daisetz Suzuki. It'll knock your socks off.
>Why settle for second-hand accounts by white boys when
>you can get the real thing? :-)
>
>
>
Right on...
Tom
ba...@galaxy.ucr.edu (John Baez) wrote in message news:<arls49$3oe$1...@glue.ucr.edu>...
> If you can imagine someone treating "Western Philosophy" as
> a single entity and indiscriminately quoting Heraclitus,
> Hegel and Nietzsche to prove that "modern physics is a lot
> like Western Philosophy", maybe you'll get what I mean.
Boris Kupershmidt in his book The Variational Principles of Dynamics
quotes Woody Allen on page 38 ; "I took a course in speed reading and
was able to read War and Peace in twenty minutes. It's about Russia."
> more substantial - maybe someone out there can suggest some
> good introductions to quantum mechanics.
For High School level introductions, there are three paperbacks that
are pretty good. The first two are in a companion set : Who Is Fourier
by Alan Gleason and the other is What Is Quantum Mechanics: A Physics
Adventure. The third is a comic book: Introducing Quantum Theory by
McEnvoy and Zarate. These three would also be good for a college
student who is totally lost in a first exposure to QM.
For university students, Pauling and Wilson's Introduction to Quantum
Mechanics is now in a Dover paperback. I saw someplace where Feynman
said that this book was the first he read followed by Dirac's
masterpiece when he was learning QM as an undergrad. Its still hard to
beat that combo. However, Shankar's Principles of Quantum Mechanics
and , as JB mentioned , Feynman's Vol. 3 is where you want to get to
as an undergrad, or someone who is interested in reading popular
articles and books about QM. There are a ton of QM texts. These above
are very slow, patient and hold you by the hand as you move through
the subject.
John Reed
"Chris Vinall" <cvi...@REMOVEihugTHIS.com.au> wrote in message
news:arhmlg$3e9$1...@lust.ihug.co.nz...
My favorite book on this subject is "The Plilosophy of Quantum Mechanics" by
Max Jammer. Now kind of dated, but I haven't seen anything that was any
better. He doesn't push any single interpretation, but gives an excellent
overview of all of them. You can pick the one that sounds best and follow
it up.
John Reed
Minhyong Kim
> Some poor uncited soul wrote:
> >Capra, F "The Tao of Physics" (I have heard accusations against this
> >book of being a bit lacking in substance)
> I loved this book in high school, but then I learned
> more physics and more philosophy, and decided it was a bit
> silly. One annoying thing about this book is that he lumps
> together all sorts of Asian philosophies as if they were one
> big undifferentiated grab-bag just waiting to be ransacked
> for quotes - a little Zen here, a little Taoism there, etc..
> If you can imagine someone treating "Western Philosophy" as
> a single entity and indiscriminately quoting Heraclitus,
> Hegel and Nietzsche to prove that "modern physics is a lot
> like Western Philosophy", maybe you'll get what I mean.
This last thesis is also probably far easier to establish
than Capra's, for obvious reasons.
Minhyong
Michael Weiss
: >I am interested in the parallels that
: >appear with Eastern mysticism and in theories like Wheeler's that implicate
: >consciousness in the basic structure of the universe, but would be equally
: >interested in books that argue against these - I am looking simply for
: >informed discussion of the subject.
I recommend "The Quantum Challenge: Modern Research on the Foundations
of Quantum Mechanics", by Greenstein and Zajonc (Jones & Bartlett,
1997).
Its strength is its careful discussion of experimental results ---
those "spooky" predictions of QM that many people find so hard to
swallow, but that are confirmed again and again by the folks who
actually go out and test them. One of the co-authors (Zajonc) was a
collaborator on one of those experiments (the "delayed choice"
experiment, proposed by Wheeler), at the Max Planck Institute.
: Finally, I am vehemently opposed to the "many-worlds"
: interpretation so I would like the book to not advocate that theory too
: enthusiastically.
I don't much like it either --- nor any of the other interpretations
that are consistent with experiment!
Laurent
"Chris Vinall" <cvi...@REMOVEihugTHIS.com.au> wrote in message
news:arhmlg$3e9$1...@lust.ihug.co.nz...
> This message is crossposted to alt.philosophy, sci.physics and
> sci.physics.research [....]
> I have a basic grasp of the Copenhagen interpretation of quantum
> mechanics and am looking to buy books which deal with the
> philosophical implications of the theory, especially as it relates
> to the measurement problem and the role of consciousness in the
> theory.
Look up - "Physics meets Philosophy at the Quantum Level" - new from
Cambridge (it is deep... very deep)
[S.p.r moderator's note: I have deleted a large amount of quoted
text. The precise title of the book is "Physics Meets Philosophy
at the Planck Scale." - jb]
Steve Carlip
> I have a basic grasp of the Copenhagen interpretation of quantum mechanics
> and am looking to buy books which deal with the philosophical implications
> of the theory, especially as it relates to the measurement problem and the
> role of consciousness in the theory. I am interested in the parallels that
> appear with Eastern mysticism and in theories like Wheeler's that implicate
> consciousness in the basic structure of the universe, but would be equally
> interested in books that argue against these - I am looking simply for
> informed discussion of the subject.
To start with, let me warn you that a lot of crap has been written on this
subject. Some of it comes from popularizers who don't understand the
science, but some comes from physicists with their own axes to grind.
(There's nothing wrong with having a strongly held point of view on the
interpretation of quantum mechanics, but there *is* something wrong
with presenting it to nonexperts as the ``truth'' and ignoring controversy.)
Let me make a few suggestions for reading:
Bell, _Speakable and unspeakable in quantum mechanics_, a wonderful
collection of essays. Pay attention to chapter 20, ``Six possible worlds
of quantum mechanics,'' to keep a bit of perspective.
Wheeler and Zurek, _Quantum theory and measurement_, a collection of
many of the classic papers.
d'Espagnat, _Conceptual foundations of quantum mechanics_. He also
has some newer books that I'm less familiar with.
Mermin, a bunch of articles in Physics Today (see the April 1985 issue for
a long one, but also his later ``Reference Frame'' columns).
Jammer has a couple of good books on the historical development of
quantum mechanics that are highly relevant to the philosophy.
Silverman, _And yet it moves_, an experimentalist's book about some of
the real observations -- you need something like this as a background,
to understand concretely what it is that you're trying to make sense of.
He's written a couple of similar books as well, which I know less about.
Feynman, _QED_, again to get a feel for the real (and strange) physics.
(Maybe Treiman, _The odd quantum_ -- I've seen very good reviews, but
have only glanced at the book.)
Finally, let me paraphrase a review I onc read of one of Capra's books.
(I wish I could remember who wrote this; it might have been Mermin, but
I'm not sure.) The reviewer said, roughly, ``If I were a Buddhist monk
and someone told me that the latest results from physics proved that my
religion was right, I'd head for the hills. I know enough about physics to
realize that there's a good chance that someone else would come along
tomorrow and say that an experimenter misread a dial, and that the
results really proved that my religion was wrong.''
Steve Carlip
Mike Dubbeld
group? I am reading and have read a number of quantum books.
I like
Elegant Universe by Brian Green it is on Superstring Theory and this
is the most likely theory that will explain quantum mechanics and is
the only theory that likes the other 3 forces with gravity I believe.
It can integrate General Relativity and Quantum Mechanics. It requires
little math background but if you have math you can appreciate his
footnotes in the back of the book.
Quantum Reality is another great book. Easy to read and Nick Herbert
is very knowledgeable in this field. Don't have to worry about math.
Another good one is The Force of Symmetry by Vincent Icke -very good
explanations. Again don't have to worry about math. But all these books
have to get you to understand the basics of physics somehow so it is
helpful knowing things like Black Body Radiation or the implications
of the Michelson-Moreley experiments say.
Tao of physics is a little old now but it is interesting. Along those
same
lines - so is One Two Theree Infinity by George Gamow. No real math
to speak of.
I also recommend Hyperspace by Michio Kaku which I have not read yet
but I read some of it and intend to read it when I get done with Elegant
Universe.
If you are not too worried about mathematics/can deal with calculus and
differntial equations and vector analysis and know what linear algebra
is
you will likely get tired of all these intuitive readings and want
something
with a little more meat (even if it is not State Space/Tensors and
Differential
Geometry). For this you might try What is Quantum Mechanics which takes
a totally off the wall approach to QM and is cartoons illustrating
mathematical
concepts to help understand QM at a deeper level without going too far.
The best one I have seen that takes a conventional approach to QM and
does
use mathematics is The Structure and Interpretation of Quantum
Mechanics
by R.I.G. Hughes. I think if you had calculus and an open mind he could
lead
you through Eigenvectors and so forth without much problem. On algebra
and trig alone the notation might bother you but it could probably be
done.
If I were you I would avoid things like -
"wave functions were in harmony".
on sci.physics. Probably the majority are died in the woods
left-brainers.
Don't forget, quantum mechanics is taught as a practical matter in
university chemistry classrooms - it is not all 'popping the wave
function.'
implications/it has a basis in fairly solid science. So to a lot of
people in
the field - they loath hearing about another philosopher talking about
some Eastern mysticism as associated with quantum mechanics. You will
find yourself slapped around likely with the above sorts of expressions.
Roger Penrose is looking at QM from a consciousness perspective and
truely one of my heros. It takes guts for Penrose to stand up to both
Neuroscience/step on their toes and catch the flack of his counterparts
in crime/physics talking about such bizzare mystical notions as
'consciousness.'
But Shadows of the Mind will reveal how science and a
deterministic/mechanistic
universe are not in the cards as a be-all-end-all - it is not a popular
place to
be as a physicist. Between Godel and Bell you have science-slapping
nightmare of an indeterminate universe - something died in the woods
hard-core realist Einsteinian physicists are not going to like no matter
how you cut it. I don't even disclose what I am doing when I ask
questions
over on sci.physics anymore so I don't pick up the troll idiot brains
comments on what is and is not physics - like they could tell me - good
one.
In fairness however sci.physics has helped me a lot/there are a lot of
people that are not brain dead.
Web Pages -
http://users.ox.ac.uk/~jrlucas/mmg.html Minds, Machines and Godel great
article along the lines Roger Penrose Shadows of the Mind pursues.
http://www.dhushara.com/book/quantcos/penrose/penr.htm Another good
one Quantum Consciousness with Penrose.
Shadows of the Mind Penrose -
http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=6ANTV
CDRH2&isbn=0195106466
Elegant Univese Amazon -
http://www.amazon.com/exec/obidos/tg/detail/-/0375708111/qid=1035952405/
sr=8-1/ref=sr_8_1/002-8442594-3104844?v=glance&n=507846
Elegant Univese Superstrings Part 1-
http://www.voting.ukscientists.com/greene.html
Quantum Reality Nick Herbert Thinking Allowed Mishlove Interview -
http://www.intuition.org/txt/herbert.htm
Quantum Reality Nick Herbert Chapter 1 He lists 8 interpretations of
Quantum Theory
http://www.kingsu.ab.ca/~brian/templeton/quantum.htm
Quantum Reality Nick Herbert another Interview -
http://www.levity.com/mavericks/herbert.htm
Is this the Copenhagen Interpretation you are reffering to
speficically? -
http://www.benbest.com/science/quantum.html
Books -
The Force of Symmetry -
http://www.amazon.com/exec/obidos/tg/detail/-/0521404959/qid=1038024645/
sr=8-2/ref=sr_8_2/103-2395048-6626252?v=glance&s=books&n=507846
the price is wrong it shows 80$ I got mine for less than 20$
The Structure and Interpretation of Quantum Mechanics -
http://www.amazon.com/exec/obidos/tg/detail/-/0674843924/qid=1038024370/
sr=8-1/ref=sr_8_1/103-1441738-0643852?v=glance&s=books&n=507846
What is Quantum Mechanics -
http://www.amazon.com/exec/obidos/tg/detail/-/0964350416/qid=1038025327/
sr=8-1/ref=sr_8_1/104-7536122-3515958?v=glance&s=books&n=507846
Hyperspace -
http://www.amazon.com/exec/obidos/tg/detail/-/0385477058/qid=1038025022/
sr=8-3/ref=sr_8_3/002-3161657-4284023?v=glance&s=books&n=507846
Strange Beauty -
http://www.amazon.com/exec/obidos/tg/detail/-/0679756884/qid=1038025893/
sr=8-1/ref=sr_8_1/002-3622141-4448049?v=glance&s=books&n=507846
The God Particle -
http://www.amazon.com/exec/obidos/tg/detail/-/0385312113/qid=1038025750/
sr=8-1/ref=sr_8_1/103-1419540-7786228?v=glance&s=books&n=507846
Faster than Light Nick Herbert -
http://www.amazon.com/exec/obidos/tg/detail/-/0452263174/qid=1038026096/
sr=1-1/ref=sr_1_1/002-3622141-4448049?v=glance&s=books
Black Holes and Time Warps - has quantum stuff in it -
http://www.amazon.com/exec/obidos/tg/detail/-/0393312763/qid=1038026346/
sr=1-1/ref=sr_1_1/002-3622141-4448049?v=glance&s=books
Oh! I did not see you had an Eastern Mysticism plug in there. Thats
where I am
comming from!!! I was selecting information speficically without
Hinduism
and so forth!
Web -
Hinduism and Quantum Mechanics -
http://www.hinduism.co.za/newpage1.htm
Has implications of Bell's Theorem 'We are all connected' - karma fits
with this.
AUM Maps vibration to creation Very good article
http://www.heartbeat2000.com/aum.htm
Hindu Cosmology -
http://www.atributetohinduism.com/Hindu_Cosmology.htm
Big Bang/Creation/Rig Veda
I have at least a 100 pages on yoga and tantra - that is my end. I
probably
have a couple of hundred yoga books.
Mike Dubbeld
Squark
> knows his stuff, and he invented a strange new way of
> thinking about it that's notoriously hard to shoot down.
Anything new since "The Quantum Theory of Motion"?
Best regards,
Squark
------------------------------------------------------------------
Write to me using the following e-mail:
Skvark_N...@excite.exe
(just spell the particle name correctly and use "com" rather than
"exe")
uno
"Chris Vinall" <cvi...@REMOVEihugTHIS.com.au> wrote in message news:<arhmlg$3e9$1...@lust.ihug.co.nz>...
>
[CUT]
>
> If you have a favourite book that isnt included in the above, by all means
> suggest it anyway. A brief rundown on the contents of any suggestion would
> be much appreciated.
>
Finkelstein, D.R. "Quantum Relativity, A Synthesis of the Ideas of
Einstein and Heisenberg", Springer.
It is really enlightening; after reading it, quantum theory does not
sound more odd or strange than the 1/r^2 Newton law. At least it
worked with me; I totally adhere to his point of view.
Wave function collapse? False problem. Inteference and uncertainty?
Couldn't be otherwise if we assume that physical acts can't be
infinitely soft and that nonetheless one can devise nontrivial
experiments succeeding with certainty (well, roughly...). Many worlds
interpretation? A matter of taste.
It actually requires some maths, but that is a fact of life if you
want to think about quantum theory. Anyway, the first few chapters are
not very demanding on this side, so I suggest you to have a look a it.
bye
Andrea Barbieri
Mattias
something like "The paradox that dissapeared, -quantum physics is strange,
but not as strange as you think".
[Sci.physics.research moderator's note: Unnecessary quoted text
deleted. The book is actually called "Where Does the Weirdness Go?
Why Quantum Mechanics is Strange, But Not as Strange as You Think". - jb]
Danny Ross Lunsford
> I dislike Bohm's approach to quantum mechanics, but he
> knows his stuff, and he invented a strange new way of
> thinking about it that's notoriously hard to shoot down.
One should also know the Bohm of "Quantum Theory" and "Special Relativity",
not just the visionary. He understood the conventional approach as well as
anyone.
-drl
Nikita
[unnecessary quoted text deleted by moderator]
> If you have a favourite book that isnt included in the above, by all means
> suggest it anyway. A brief rundown on the contents of any suggestion would
> be much appreciated.
Try:
Heidegger, Martin "Being and Time"
Sartre, Jean-Paul "Being and Nothingness"
Heisenberg, Werner "Physics and Philosophy"
Dan Riley
> Mermin, a bunch of articles in Physics Today (see the April 1985 issue for
> a long one, but also his later ``Reference Frame'' columns).
Some of these (and other Mermin writings) can be found in his
book "Boojums all the Way Through".
-dan
Aaron Bergman
wrote:
> I dislike Bohm's approach to quantum mechanics, but he
> knows his stuff, and he invented a strange new way of
> thinking about it that's notoriously hard to shoot down.
It's quite easy to shoot down: just mention special relativity.
Aaron
--
Aaron Bergman
<http://www.princeton.edu/~abergman/>
Urs Schreiber
> In article <arls49$3oe$1...@glue.ucr.edu>, ba...@galaxy.ucr.edu (John Baez)
> wrote:
>
>> I dislike Bohm's approach to quantum mechanics, but he
>> knows his stuff, and he invented a strange new way of
>> thinking about it that's notoriously hard to shoot down.
>
> It's quite easy to shoot down: just mention special relativity.
Entering the KG equation with a wave function in polar form and seperating
real and imaginary part gives the relativistic continuity equation
together with the relativistic Hamilton-Jacobi equation plus a term
proportional to hbar.
Eric Dennis
> > I dislike Bohm's approach to quantum mechanics, but he
> > knows his stuff, and he invented a strange new way of
> > thinking about it that's notoriously hard to shoot down.
>
> It's quite easy to shoot down: just mention special relativity.
I guess you mean that Bohm's interpretation of the non-relativistic
Schrodinger equation is, well, non-relativistic. Not a surprise. If
you are genuinely interested in determining whether a relativistic
analog exists -- your comment suggests otherwise -- one is described
in "Beables for quantum field theory" in Bell's collection *Speakable
and unspeakable in quantum mechanics*.
Alfred Einstead
> I have a basic grasp of the Copenhagen interpretation of quantum mechanics
Do you, though? Of its full import?
> I am vehemently opposed to the "many-worlds" interpretation so I would
> like the book to not advocate that theory too enthusiastically.
"Many worlds" is just a fancy way of saying "mixed state". If you
were to ask me what a bunch of parallel worlds were, I'd probably
describe it as a conglomeration of worlds, each given a weight,
with all the weights adding up to 1. That's just what we call a
mixed state.
A theory that incorporates a process for going from a pure state
to a mixed state is ipso facto a many worlds theory. Copenhagen
does so, under the standard von Neumann axiomatization (Evolution
+ Projection) by the Projection postulate.
So, Copenhagen is a many worlds theory. What starts out as a
pure state, after 1, 2, 3 or more measurements (i.e. applications
of the Projection postulate) ends up as a mixed state.
Everett, on the other hand, goes from pure state to pure state
and has no process for pure state -> mixed state. So, Everett
is NOT a many world's theory.
The distinction, by the way, has nothing to do with Quantum
Physics. Classical Physics also have a notion of pure states
and mixed states. But the usual theory a' la Newton always
goes from pure state to pure state. However, Statistical
Mechanics makes ESSENTIAL use of the concept of mixed state.
There's no way to base Statistical Physics upon the classical
notion of a pure state (because the entropy of a macro state
would then be infinite).
So, classical Statistical Mechanics is actually a many worlds
theory. A classical one -- which only serves to illustrate
that the concept has nothing per se to do with Quantum Physics.
Alfred Einstead
> A bit!!! Capra's argument goes like this. "here is a quote from a 20th
> century physicist, here is a quote translated from a tibetan monk from
> the 10th century. The translation uses a word of three or more
> syllables, and the physicist uses exactly the same word! therefore
> modern physicists and ancient Eastern mystics are saying exactly the
> same thing".
Well, usually when you use the same words you mean the same thing.
For example, if I say "I'm all out of bubble gum", I normally don't
mean by this that I'm about to shoot up a bank because I think
there's a bunch of alien beings inside it! And at the same time,
if someone else also says "I'm all out of bubble gum", it means
the very same thing as when I said it! And they're not going to
be shooting up a bank either.
Likewise, if modern physicists are stumbling onto concepts that
have found strong foreshadowing in ancient philosophy, it's
certainly not just a case of "oh, they were just using the
same words. They didn't REALLY mean the same thing. Poo poo.",
but more often a case of "the concepts which have proven critical
to the rendering of certain modern notions in physics have, in fact,
been well understood and well studied in ancient lore. We just
forgot about them until now or didn't clearly understand them
until now because it's not something we normally encounter within
our philosophical tradition."
Peter Shor
ede...@princeton.edu (Eric Dennis) wrote in message news:<ef463682.02121...@posting.google.com>...
I actually know relatively little about Bohm's theories, so I could be
completely wrong about this. Can anybody who knows what they're talking
about verify this?
Anyway, I was under the apprehension that while special relativity could
be incorporated into a Bohmian approach, the resulting physical theory
was not Lorenz-invariant (although it would appear so to any observer
within the system). This apparently seriously disturbs some people,
but not others; and this is the source of the claim that Bohm's theory
can't incorporate special relativity.
Peter Shor
nobody
Peter Shor wrote:
> [Eric Dennis wrote:]
> > Aaron Bergman <aber...@princeton.edu> wrote:
> >
> > > > I dislike Bohm's approach to quantum mechanics, but he
> > > > knows his stuff, and he invented a strange new way of
> > > > thinking about it that's notoriously hard to shoot down.
> > >
> > > It's quite easy to shoot down: just mention special relativity.
> >
> > I guess you mean that Bohm's interpretation of the non-relativistic
> > Schrodinger equation is, well, non-relativistic. Not a surprise. If
> > you are genuinely interested in determining whether a relativistic
> > analog exists -- your comment suggests otherwise -- one is described
> > in "Beables for quantum field theory" in Bell's collection *Speakable
> > and unspeakable in quantum mechanics*.
>
> I actually know relatively little about Bohm's theories, so I could be
> completely wrong about this. Can anybody who knows what they're talking
> about verify this?
The theory set forth in Bohm's 1952 papers (Phys. Rev. 85, 166 and 180)
is mathematically equivalent to non-relativistic quantum mechanics.
Its distinguishing elements are that it assumes that particle positions
assume definite (but random) values at all times, and that it requires
all measurement results to be representable as the position of something
(like a pointer on a measuring instrument). A free bosonic field theory
can also be handled (as Bohm points out in an appendix to the second
paper) by quantizing its normal modes as harmonic oscillators and then
treating the oscillators via Bohm's equivalent to QM (with oscillator
amplitudes being treated as a coordinates).
The theory of Bell's described in "Beables for quantum field theory"
is based on field theory in a discrete space, and is similar to Bohm's
1952 theory in that it also postulates a set of preferred variable
that assume definite (but random) values at all times, and requires
all measurement results to be represented as values of these preferred
variables. The preferred variables in this case are fermion number
density at each point in space, rather than particle positions.
> Anyway, I was under the apprehension that while special relativity could
> be incorporated into a Bohmian approach, the resulting physical theory
> was not Lorenz-invariant (although it would appear so to any observer
> within the system).
That is correct. Bell's theory, for instance, is not Lorentz invariant
because the preferred variables presuppose the choice of a specific
reference frame. The same is true of Bohm's treatment of free bosonic
fields. Observational results, however, are independent of the choice
of reference frame, provided that the underlying field equations are
Lorentz invariant.
> This apparently seriously disturbs some people, but not others; and this
> is the source of the claim that Bohm's theory can't incorporate special
> relativity.
I think that this hits the nail right on the head. As I stated in article
<2002121620...@localhost.localdomain>,
> I _do_ agree that there is a great deal of arbitrariness in singling
> out position for special treatment (it's assumed in Bohmian mechanics
> to have a definite, objective value at all times); from a mathematical
> point of view, one could have just as well singled out momentum as
> primary and required all measurements to be reducible to observations
> of momentum. In addition, there are _many_ alternatives to the
> de Broglie-Bohm trajectory equation that yield observationally
> equivalent results. In this regard I tend to view the relationship
> between Bohmian mechanics and versions of standard quantum mechanics
> that have no collapse as something like the relationship between
> Lorentz Ether Theory and Special Relativity: the former postulates
> a preferred reference frame [analogous to preferred dynamical
> variables] while the latter does not, but the two are observationally
> equivalent.
nobody
Charles Francis
In message <e58d56ae.0212...@posting.google.com>, Alfred
Einstead <whop...@csd.uwm.edu> writes
>Charles Francis <cha...@clef.demon.co.uk> wrote:
>> A bit!!! Capra's argument goes like this. "here is a quote from a 20th
>> century physicist, here is a quote translated from a tibetan monk from
>> the 10th century. The translation uses a word of three or more
>> syllables, and the physicist uses exactly the same word! therefore
>> modern physicists and ancient Eastern mystics are saying exactly the
>> same thing".
>
>Well, usually when you use the same words you mean the same thing.
So any two sentences containing the word "a" mean exactly the same
thing? So I if say "that car is green" and "the grass is green" that
means that cars and grass are the same thing?
>Likewise, if modern physicists are stumbling onto concepts that
>have found strong foreshadowing in ancient philosophy,
.... <snip>
If they were, but they haven't and they aren't. That is a big if. These
were mystic philosophers and the things they were talking about were
things of the mind, things which are, by definition, not even studied by
modern physicists.
Oh sure, at about that time when Capra was published and I was doing my
doctorate, I was also taking an interest in TM, Gurdjieff, Lao Tse,
Sufism, Zen, even Castaneda (and I have never met anyone from any
philosophy who really understood Journey to Ixtlan, a story of drug
taking it is not!). And Bohm's "Wholeness and the Implicate Order" had a
title which captured the imagination of those members of the educated
middle class who like to think they are the cognoscenti. Of course they
didn't understand a word of it, and many of them came to ask me, so I
know.
It was just after the Hippies, and Journey to the East (Herman Hesse)
had been the bible of the original acid freaks. Gell-Mann had even
called the baryon octet "the eightfold way". So because it has the same
name does that mean that the octet is same thing as the advice given by
the Gautama Buddha on the road to Nirvana? And how come the decuplet is
not called the "ten commandments"?
Actually I have often wondered how many bible bashing Americans would
find it deeply offensive if the decuplet had been called "the ten
commandments", and why calling the octet "the eightfold way" should be
any less offensive to the even more numerous Buddhists world wide.
But I remember the meeting of Maharishi (the head of the TM movement)
with a bunch of third rate physicists, and the conversations between
them, and Maharishi sitting with a huge stupid grin nodding his head and
making remarks, and all his followers bowing down and saying "isn't
Maharishi amazing, he understands all this physics without any training
or education" and meditating even more fervently so as to gain some
insight. Of course Maharishi didn't understand a word of it. I was
making a practice of meditation at the time, and I must say the whole
sorry spectacle did a lot to turn me off the TM movement. Don't get me
wrong, TM is a good trick, and with all sorts of benefits to health and
happiness, but the road to an instant understanding of research into
physics it is not!
>but more often a case of "the concepts which have proven critical
>to the rendering of certain modern notions in physics have, in fact,
>been well understood and well studied in ancient lore.
But they haven't. Once you understand these concepts they have actually
nothing in common whatsoever. Only some of the words are similar.
>We just
>forgot about them until now or didn't clearly understand them
>until now because it's not something we normally encounter within
>our philosophical tradition."
Was this last para a quote from "the Tao of Physics"? There simply is no
case for what you say, even if it does sound like a nice idea. Actually
it would make a darn sight more sense to realise that this stuff is very
much in our philosophical tradition, only we still don't understand it
clearly, and because we don't understand it we don't recognise it. There
is far more in common between Berkeley's idealism and Eastern mysticism.
At least the subject area is much the same. Plato, so dominant in the
western tradition is also regarded as at the head of the Sufis.
But mostly we do at least understand Berkeley well enough to notice that
he is not saying the same thing modern physics. Likewise our own western
monks have been meditating in our own western monasteries for centuries.
Only they call it prayer. True prayer is not what we are taught as
children, but something deep and mystical. I know because I was brought
up by monks, and I was originally taught to meditate, or pray, by one of
them. I learned TM because I wanted to understand it better, because the
idea of "personal communion with God" was too much of a head trip, and I
wanted a more secular angle. And it is basically exactly the same thing
as I was taught by the monk.
So, if anyone want a layman's understanding of physics, choose a book
which is designed to do that, like Gribbin, or one written by a
physicist, preferably Feynman; even Paul Davies isn't too bad. Frank
Close wrote a really nice book on Quarks called the Cosmic Onion, if you
can find it. And if you want an understanding of mystic philosophy, read
books by mystic philosopher's, like John Baez says, why get it third
hand from white kids who don't understand it like Zukav and Capra, when
you can buy Idries Shah, and Suzuki? It may well be that mystic
philosophy is the same the world over, and in all ages. Mystic
philosophers have always said so. Indeed a Zen monk, on reading the
sermon on the mount stated "this man is approaching enlightenment". But
mystic philosophy is not physics, whatever words are used, and does not
contain the same ideas.
Regards
--
Charles Francis
Eric Dennis
nobody <nob...@localhost.ucar.edu> wrote:
> > I _do_ agree that there is a great deal of arbitrariness in singling
> > out position for special treatment (it's assumed in Bohmian mechanics
> > to have a definite, objective value at all times); from a mathematical
> > point of view, one could have just as well singled out momentum as
> > primary and required all measurements to be reducible to observations
> > of momentum.
It is true that you can formulate analogs of Bohmian mechanics in
different bases (e.g. momentum), but I don't think the choice of the
position basis is so arbitrary. A similar choice is made when taking
the Hamiltonian of a given theory to be local in space. Why should it
be local in position space and not momemtum space? There is clearly
something physically special about position space. It is only that
transformation theory tends to obscure the abstract character of the
other spaces.
> > In addition, there are _many_ alternatives to the
> > de Broglie-Bohm trajectory equation that yield observationally
> > equivalent results. In this regard I tend to view the relationship
> > between Bohmian mechanics and versions of standard quantum mechanics
> > that have no collapse as something like the relationship between
> > Lorentz Ether Theory and Special Relativity: the former postulates
> > a preferred reference frame [analogous to preferred dynamical
> > variables] while the latter does not, but the two are observationally
> > equivalent.
That is an interesting analogy, although I think the conceptual
problems with those interpretations (I assume you're primarily
referring to Many Worlds) are much more serious than anything that
could be raised against SR.
Back to the original issue, it may also be possible to formulate a
convincing Lorentz invariant Bohm-type theory by introducing
additional structure (e.g. a foliation). See "Hypersurface Bohm-Dirac
models" quant-ph/9801070. As they admit, it doesn't count as serious
Lorentz invariance unless the additional structure is plausibly
dynamical rather than just background, and that hasn't been
accomplished yet. A different, more speculative proposal for Lorentz
invariance without any additional structure is given in
quant-ph/0105040. (Personally, I don't see the point in clinging to
serious Lorentz invariance when we know that serious relativistic
locality is belied by EPR-Bell experiments. It seems much more likely
that Lorentz invariance is simply an emergent symmetry.)
Danny McCarty
>From: whop...@csd.uwm.edu (Alfred Einstead)
>Date: 12/18/2002 8:50 PM Central Standard Time
>Message-id: <e58d56ae.02121...@posting.google.com>
>
>"Chris Vinall" <cvi...@REMOVEihugTHIS.com.au> wrote:
>
>> I am vehemently opposed to the "many-worlds" interpretation so I would
>> like the book to not advocate that theory too enthusiastically.
>
>"Many worlds" is just a fancy way of saying "mixed state". If you
>were to ask me what a bunch of parallel worlds were, I'd probably
>describe it as a conglomeration of worlds, each given a weight,
>with all the weights adding up to 1. That's just what we call a
>mixed state.
>
>A theory that incorporates a process for going from a pure state
>to a mixed state is ipso facto a many worlds theory. Copenhagen
>does so, under the standard von Neumann axiomatization (Evolution
>+ Projection) by the Projection postulate.
>
>So, Copenhagen is a many worlds theory. What starts out as a
>pure state, after 1, 2, 3 or more measurements (i.e. applications
>of the Projection postulate) ends up as a mixed state.
>
>Everett, on the other hand, goes from pure state to pure state
>and has no process for pure state -> mixed state. So, Everett
>is NOT a many world's theory.
Are you sure you understand Evertt? As I understand it, he is saying that
there is no "mixed state", but that rather ALL of the possible consequences
actually happen and exist as pure states, upteen trillions of uncountable
quadrillions of them by now.... of course, they do not interact with us in this
particualr pure state so we cannot detect them.
[Moderator's note: Unnecessary quoted text deleted...
I think that Alfred Einstead understands this, but considers the
situation described to be something other than a "many worlds"
hypothesis, by his definition of the phrase. To each his own.
Note that Everett actually called his interpretation
the "relative state interpretation"; "many worlds" was a phrase
used by others. -MM]
me...@cars3.uchicago.edu
>Charles Francis <cha...@clef.demon.co.uk> wrote:
>> A bit!!! Capra's argument goes like this. "here is a quote from a 20th
>> century physicist, here is a quote translated from a tibetan monk from
>> the 10th century. The translation uses a word of three or more
>> syllables, and the physicist uses exactly the same word! therefore
>> modern physicists and ancient Eastern mystics are saying exactly the
>> same thing".
>
>Well, usually when you use the same words you mean the same thing.
We use the word "electron" and so did the ancient Greeks. It did not
mean the same thing, though.
Mati Meron | "When you argue with a fool,
me...@cars.uchicago.edu | chances are he is doing just the same"
Thinh Tran
"Chris Vinall" <cvi...@REMOVEihugTHIS.com.au> wrote in message news:<arhmlg$3e9$1...@lust.ihug.co.nz>...
>
> This message is crossposted to alt.philosophy, sci.physics and
> alt.philosophy.* or sci.physics.* that seem directly appropriate (the lack
> of sci.physics.quantum seems especially strange). Apologies in advance if
> this is going to inappropriate groups.
>
> of the theory, especially as it relates to the measurement problem and the
> role of consciousness in the theory. I am interested in the parallels that
> appear with Eastern mysticism and in theories like Wheeler's that implicate
> consciousness in the basic structure of the universe, but would be equally
> interested in books that argue against these - I am looking simply for
> informed discussion of the subject.
I strongly recommend the following two books which were very helpful
to me:
QED - the strange theory of light and matter, Richard Feynman, 1988
The Emperor's New Mind, Roger Penrose, 1989 (or 2nd ed. 1999)
1. Both of these books deal with philosophical implications of QM
(although Feynman was known to have always looked down on opinions of
philosophers on scientific matters.)
2. Both were written by the best in the field. There is no risk
of being misinformed (which, believe it or not, is a very high risk
these days when you read books written by 'certified experts'.)
3. Both were scholarly written, but not too difficult for even
laymen.
Regrettably there is nothing about eastern mysticism in these two
books. With my oriental background I wasn't impressed with how the Tao
of Physics or the Dancing Wuli Masters fused QM with eastern
mysticism. I don't think the authors were dishonest or tried to fit
the New Age sensationalism. I just think they didn't know enough of
eastern mysticism.
(However, if you can wait 5 years for my book you will see that there
is a very meaningful connection between science and eastern mysticism.
I promise that this book is worth the wait.)
Thinh Tran (http://www.thinhtran.com)
Ilja Schmelzer
>> Anyway, I was under the apprehension that while special relativity could
>> be incorporated into a Bohmian approach, the resulting physical theory
>> was not Lorenz-invariant (although it would appear so to any observer
>> within the system).
>
> That is correct. Bell's theory, for instance, is not Lorentz invariant
> because the preferred variables presuppose the choice of a specific
> reference frame. The same is true of Bohm's treatment of free bosonic
> fields. Observational results, however, are independent of the choice
> of reference frame, provided that the underlying field equations are
> Lorentz invariant.
>
>> This apparently seriously disturbs some people, but not others;
An interesting question is why it disturbs at all. A hidden variable
theory contains, among others, a well-known classical hidden variable
- the preferred frame. If somebody is not disturbed by hidden
variables in principle, why should he be disturbed by a preferred
frame?
>> and this is the source of the claim that Bohm's theory can't
>> incorporate special relativity.
> I think that this hits the nail right on the head.
There is another misunderstanding which may be a source of such
claims. There are known difficulties with a particle picture in QFT.
If somebody naively believes that Bohmian theory should be based on
particle trajectories, he may believe that BM cannot be generalized to
QFT.
But, of course, to "bohmianize" QFT one has to use a Bohmian field
theory, where the configuration space Q is some space of fields
{g_ij(x),A_i(x),psi(x)} and the wave function Psi(Q) becomes a
functional. No particle picture is necessary to do this.
Ilja
--
I. Schmelzer, <il...@ilja-schmelzer.net> , http://ilja-schmelzer.net
Thinh Tran
Comment: I'm afraid your defintion of "many-worlds interpretation"
(MWI) for QM is non-standard.
My understanding is that MWI was devised to work around a logical
difficulty in QM (of the many possibilities, only 1 takes place. Why?)
When, say, path D is taken by a particle QM has to answer the
question "why path D? -and not A, B, C, E, F,..., etc." The natural
answer may be whatever (least resistance, minimum energy, etc., i.e.
some sort of definition for 'the best path') but none can be
considered satisfactory because the next question will be "How does
the quantum thing knows that the path it chose was 'the best path'?"
(The Copenhagen Interpretation avoided this question from being
raised by accepting a mixed state, interpreted macroscopically as "the
cat is both dead and alive before we open the cage and observe it".)
But once the question has been asked, there are only two (known)
logical solutions:
1. Instantaneous (and sometimes backward) communications among
all paths.
2. All paths are taken by the particle, but in different worlds
(our world happens to be one of them.)
By ruling out solution 1, we are left with solution 2.
This, I believe, is the standard meaning of MWI, as championed by
Everett in 1957. If this is incorrect please explain. I appreciate it.
If I may, I would like to add that I disagree with MWI (as I
understand it).
Thinh Tran (http://www.thinhtran.com)
nobody
Eric Dennis wrote:
> nobody <nob...@localhost.ucar.edu> wrote:
[ ... ]
> > In addition, there are _many_ alternatives to the
> > de Broglie-Bohm trajectory equation that yield observationally
> > equivalent results. In this regard I tend to view the relationship
> > between Bohmian mechanics and versions of standard quantum mechanics
> > that have no collapse as something like the relationship between
> > Lorentz Ether Theory and Special Relativity: the former postulates
> > a preferred reference frame [analogous to preferred dynamical
> > variables] while the latter does not, but the two are observationally
> > equivalent.
>
> That is an interesting analogy, although I think the conceptual
> problems with those interpretations (I assume you're primarily
> referring to Many Worlds) are much more serious than anything that
> could be raised against SR.
Actually, what I was referring to was the fact that the de Broglie-Bohm
guiding equation -- that is, the differential equation that governs
particle trajectories in that theory -- is vastly under-determined
by the data. The only requirement is that it the particle position
probability distribution be equal to the absolute square of the
quantum-mechanical wave function at all times given that it is at
some initial time. All that is constrained here is the first-order
probability distribution, but in to fully specify the trajectories one
would in general also need to specify joint probability distributions
for positions at different times, a point on which quantum mechanics
typically is silent. Many different trajectory equations will do
the job, some deterministic, others stochastic. Deotto and Ghirardi
discuss some alternatives for deterministic trajectories in
quant-ph/9704021; Bacciagaluppi does the same thing for stochastic
trajectories in quant-ph/9811040.
nobody
Torquemada
> My understanding is that MWI was devised to work around a logical
> difficulty in QM (of the many possibilities, only 1 takes place. Why?)
I don't believe that is the case. Many MWI sympathetic physicists are
entirely happy with the idea of a non-deterministic system and see no issue
with having to pick one outcome of many. I don't remember anything about
this "logical" difficulty in Everett's original paper. The reason many
people like MWI is that it removes the projection/collapse hypothesis from
quantum mechanics and that they believe that (1) you've simplified the
physics by only having one type of time evolution (the Schrodinger equation)
and (2) you can predict that individual observers will still see the kinds
of collapse-like things we see in labs.
PS Many people think (2) isn't true and that (1) pays for the simplification
by complexification elsewhere but that's not relevant to the point that I am
making.
michaelprice
Anyone who wants to know what many-worlds really is
all about should read
http://www.hedweb.com/manworld.htm
Many-worlds is not a mixed state, as Albert Einstead
believes, although he is correct when he states
> Everett, on the other hand, goes from pure state to pure
> state and has no process for pure state -> mixed state.
although that was probably the only correct statement
in his post.
Cheers,
Michael C Price
----------------------------------------
http://mcp.longevity-report.com
http://www.hedweb.com/manworld.htm
Mark
michaelprice" <michae...@ntlworld.com> writes:
>Many-worlds is not a mixed state, as Albert Einstead
>believes,
(The statement made was a conclusion, not a belief).
You mean: that what is often CALLED "many worlds" doesn't involve
mixed states, but the name is a very misleading misnomer and is
widely regarded as such because the concept of the mixed state
provides the more correct and appropriate formalization of
what one normally means by many worlds.
Consequently, one often hears alternate names like "many observers" or
"many minds" used in place of "many worlds". Everett, himself,
never made any direct reference to any such thing as many worlds
and his original paper doesn't even read like that. The notion
of relative states has nothing to do with anything that even
resembles "many worlds" in any sense of the term.
>> Everett, on the other hand, goes from pure state to pure
>> state and has no process for pure state -> mixed state.
>although that was probably the only correct statement
>in his post.
.. which is why the relative state formulation is not a many
worlds theory at all.
Oz
Thinh Tran <thinhv...@cs.com> writes
> 1. Instantaneous (and sometimes backward) communications among
>all paths.
> 2. All paths are taken by the particle, but in different worlds
>(our world happens to be one of them.)
> By ruling out solution 1, we are left with solution 2.
Hmmm. From my position of infinite ignorance I have for a while rather
been coming down on both (1) *and* (2). This is despite (or possibly
because of) my lack of knowledge on everett and bohm.
Entanglement seems to allow no other alternative but that (1) exists.
However the macroscopic entanglement as usually described seems to only
be observed in very carefully prepared particle pairs (or groups) that
are in some way isolated from the rest of the universe. That is, they
only show entanglement when they do not interact with anything.
Equally any wavelike behaviour implies a particle is spread out over
space. In that case it can and probably does take many paths
simultaneously.
I am beginning to wonder if this is not too simplistic and that in
reality it is spread over spacetime. I haven't thought about this very
deeply as yet but from my overly-simplistic background it might be that
the non-commutation of position and momentum might be simply seen as a
single 4-D property. Project it on three space dimensions and you call
it 'position', project it on two space and one time and you call it
'momentum' in the -direction. Hardly surprising the two do not commute.
--
Oz
This post is worth absolutely nothing and is probably fallacious.
Note: soon (maybe already) only posts via despammed.com will be accepted.
Eric Dennis
> > That is an interesting analogy, although I think the conceptual
> > problems with those interpretations (I assume you're primarily
> > referring to Many Worlds) are much more serious than anything that
> > could be raised against SR.
>
> Actually, what I was referring to was the fact that the de Broglie-Bohm
> guiding equation -- that is, the differential equation that governs
> particle trajectories in that theory -- is vastly under-determined
> by the data. The only requirement is that it the particle position
> probability distribution be equal to the absolute square of the
> quantum-mechanical wave function at all times given that it is at
> some initial time. All that is constrained here is the first-order
> probability distribution, but in to fully specify the trajectories one
> would in general also need to specify joint probability distributions
> for positions at different times, a point on which quantum mechanics
> typically is silent. Many different trajectory equations will do
> the job, some deterministic, others stochastic. Deotto and Ghirardi
> discuss some alternatives for deterministic trajectories in
> quant-ph/9704021; Bacciagaluppi does the same thing for stochastic
> trajectories in quant-ph/9811040.
I'm aware of this under-determination. My point was that the thing
corresponding to the non-trajectory interpretations in your analogy,
namely SR, is not nearly as questionable as most of these
non-trajectory interpretations. ``Serious'' SR locality faces external
challenges (EPR-Bell experiments etc.), but Many Worlds, Copenhagen,
and other non-trajectory interpretations suffer from internal logical
difficulties no matter what the experimental situation is.
Gordon D. Pusch
ede...@princeton.edu (Eric Dennis) writes:
> (Personally, I don't see the point in clinging to
> serious Lorentz invariance when we know that serious relativistic
> locality is belied by EPR-Bell experiments.
We know no such thing. What we know is that _Bell's inequality_ is in
conflict with experiment. Since Bell's inequality presupposes some very
naive interpretations of both "locality" and "realism," makes unjustifiable
assumptions about the nature and influence of the hypothetical "hidden
variables," an unjustified hypothesis of "counterfactual definiteness,"
uses a sloppy mathematical notation that fails to clearly distinguish
between joint and conditional probabilities, and presupposes Popper's
untenable "propensity" interpretation of probability, which falsely
conflates "causation" with conditioning, and as a result fails to satisfy
Bayes' Theorem when applied to events that occur at different times,
IMO your obituary for locality is MUCH more than a little premature.
See pp.9--13 of Jaynes' "Clearing up mysteries: The original goal,"
<http://bayes.wustl.edu/etj/articles/cmystery.pdf>,
<http://bayes.wustl.edu/etj/articles/cmystery.ps>.
-- Gordon D. Pusch
perl -e '$_ = "gdpusch\@NO.xnet.SPAM.com\n"; s/NO\.//; s/SPAM\.//; print;'
nobody
> [ ... ] Bell's inequality presupposes some very
>naive interpretations of both "locality" and "realism," makes unjustifiable
>assumptions about the nature and influence of the hypothetical "hidden
>variables," an unjustified hypothesis of "counterfactual definiteness,"
>uses a sloppy mathematical notation that fails to clearly distinguish
>between joint and conditional probabilities, and presupposes Popper's
>untenable "propensity" interpretation of probability, which falsely
>conflates "causation" with conditioning, and as a result fails to satisfy
>Bayes' Theorem when applied to events that occur at different times,
>IMO your obituary for locality is MUCH more than a little premature.
>See pp.9--13 of Jaynes' "Clearing up mysteries: The original goal,"
><http://bayes.wustl.edu/etj/articles/cmystery.pdf>,
><http://bayes.wustl.edu/etj/articles/cmystery.ps>.
You've cited that article before, and we've criticized it before, right
here on this newsgroup. See, for example,
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&safe=off&th=91a6dc7c2d62fbdf&rnum=1
Jaynes has produced some very good works, but this paper is not one
of them.
nobody
Michael C Price
Mark, hope you find this useful:
Q33 Is Everett's relative state formulation the same as many-worlds?
Yes, Everett's formulation of the relative state metatheory is the
same as many-worlds, but the language has evolved a lot from Everett's
original article [2] and some of his work has been extended,
especially in the area of decoherence. (See "What is decoherence?")
This has confused some people into thinking that Everett's "relative
state metatheory" and DeWitt's "many-worlds interpretation" are
different theories.
Everett [2] talked about the observer's memory sequences splitting to
form a "branching tree" structure or the state of the observer being
split by a measurement. (See "What is a measurement?") DeWitt
introduced the term "world" for describing the split states of an
observer, so that we now speak of the observer's world splitting
during the measuring process. The maths is the same, but the
terminology is different. (See "What is a world?")
Everett tended to speak in terms of the measuring apparatus being
split by the measurement, into non-interfering states, without
presenting a detailed analysis of *why* a measuring apparatus was so
effective at destroying interference effects after a measurement,
although the topics of orthogonality, amplification and
irreversibility were covered. (See "What is a measurement?", "Why do
worlds split?" and "When do worlds split?") DeWitt [4b], Gell-Mann and
Hartle [10], Zurek [7a] and others have introduced the terminology of
"decoherence" (See "What is decoherence?") to describe the role of
amplification and irreversibility within the framework of
thermodynamics.
--------------------------------------------------------------------------------
Q34 What is a relative state?
The relative state of something is the state that something is in,
conditional upon, or relative to, the state of something else. What
the heck does that mean? It means, amongst other things, that states
in the same Everett-world are all states relative to each other. (See
"Quantum mechanics and Dirac notation" for more precise details.)
Let's take the example of Schrodinger's cat and ask what is the
relative state of the observer, after looking inside the box? The
relative state of the observer (either "saw cat dead" or "saw cat
alive") is conditional upon the state of the cat (either "dead" or
"alive").
Another example: the relative state of the last name of the President
of the Unites States, in 1995, is "Clinton". Relative to what?
Relative to you and me, in this world. In some other worlds it will be
"Bush", "Smith", etc. ....... Each possibility is realised in some
world and it is the relative state of the President's name, relative
to the occupants of that world.
According to Everett almost all states are relative states. Only the
state of the universal wavefunction is not relative but absolute.
--------------------------------------------------------------------------------
Q35 Was Everett a "splitter"?
Some people believe that Everett eschewed all talk all splitting or
branching observers in his original relative state formulation [2].
This is contradicted by the following quote from [2]:
[...] Thus with each succeeding observation (or interaction), the
observer state "branches" into a number of different states. Each
branch represents a different outcome of the measurement and the
corresponding eigenstate for the object- system state. All branches
exist simultaneously in the superposition after any given sequence of
observations.[#] The "trajectory" of the memory configuration of an
observer performing a sequence of measurements is thus not a linear
sequence of memory configurations, but a branching tree, with all
possible outcomes existing simultaneously in a final superposition
with various coefficients in the mathematical model. [...]
[#] Note added in proof-- In reply to a preprint of this article some
correspondents have raised the question of the "transition from
possible to actual," arguing that in "reality" there is-as our
experience testifies-no such splitting of observers states, so that
only one branch can ever actually exist. Since this point may occur to
other readers the following is offered in explanation.
The whole issue of the transition from "possible" to "actual" is taken
care of in the theory in a very simple way- there is no such
transition, nor is such a transition necessary for the theory to be in
accord with our experience. From the viewpoint of the theory all
elements of a superposition (all "branches") are "actual," none are
any more "real" than the rest. It is unnecessary to suppose that all
but one are somehow destroyed, since all separate elements of a
superposition individually obey the wave equation with complete
indifference to the presence or absence ("actuality" or not) of any
other elements. This total lack of effect of one branch on another
also implies that no observer will ever be aware of any "splitting"
process.
Arguments that the world picture presented by this theory is
contradicted by experience, because we are unaware of any branching
process, are like the criticism of the Copernican theory that the
mobility of the earth as a real physical fact is incompatible with the
common sense interpretation of nature because we feel no such motion.
In both case the arguments fails when it is shown that the theory
itself predicts that our experience will be what it in fact is. (In
the Copernican case the addition of Newtonian physics was required to
be able to show that the earth's inhabitants would be unaware of any
motion of the earth.)
-------------------------------------------------
whop...@alpha2.csd.uwm.edu (Mark) wrote in message news:<aufsge$4hc$1...@uwm.edu>...
Cheers,
Michael C Price
----------------------------------------
http://www.hedweb.com/manworld.htm
Michael C Price
> 2. All paths are taken by the particle, but in different
> worlds (our world happens to be one of them.)
> By ruling out solution 1, we are left with solution 2.
> This, I believe, is the standard meaning of MWI, as
> championed by Everett in 1957. If this is incorrect please
> explain. I['d] appreciate it.
Provided we are careful about the definition of "world"
then your description matches my understanding of MWI.
> If I may, I would like to add that I disagree with MWI
> (as I understand it).
Do you disgree because you don't like it (most people don't)
or because you believe it as flawed (as are the other
interpretations)? I believe in it because I believe it is
not flawed, whereas all the other interpretations are flawed.
My detailed reasons are explained in
http://www.hedweb.com/manworld.htm
Cheers,
Michael C Price
----------------------------------------
http://mcp.longevity-report.com
http://www.hedweb.com/manworld.htm
Ilja Schmelzer
Thanks for this reference. I highly value Jaynes for his Probability
theory book http://bayes.wustl.edu/etj/prob/book.ps, but here he has
not understood the seriousness of a violation of Bell's inequality.
Certainly Bell has not made the elementary error of conflating
causation with conditioning.
BTW I have a question about the connection between the Bayesian and
Kolmogorov approach. AFAIU Jaynes refers on p.44 of
bayes.wustl.edu/etj/prob/book.ps, a Kolmogorov theory fulfils also the
"consistent reasoning" axioms of Bayesian probability theory. What
about the reverse direction? It seems to me that for a given Baysian
set of statements A_i with consistent probabilities P(A_i) we can also
construct a (rather artificial) set of "elementary statements" so that
the theory fulfills Kolmogorovs axioms on this set (deeply forgotten
unclear memories about maximal elements, axiom of choice, forcing
method appear in my mind, suggesting me that this should be elementary
stuff for people with fresh memories about this domain).
Is there anything in this direction, possibly in the not webbed
appendix A of bayes.wustl.edu/etj/prob/book.ps?
Eric Dennis
Jaynes has many incisive things to say about the role of probability
in physics; however, I believe he has uncharacteristically fumbled the
ball in regard to the issue of Bell inequalities. His first basic
objection is that Bell's assumption
P(A|a,b,lambda) = P(A|a,lambda)
is untenable even if we posit no physical influence from the b-device
setting to the A-measurement result. He formulates his objection as an
anology with an urn containing red and white balls from which we we
are to make two draws in succession. He says the above equation is
analogous to
P(draw 1 is red | draw 2 is red, U) = P(draw 1 is red | U)
with the analogous justification that since the outcome of draw 2
cannot causally influence the outcome of draw 1, the former may be
omitted from the conditioning statements. (Above, "U" just indicates
facts about the urn.)
Indeed this omission is invalid, but only because draw 1 can causally
influence draw 2. Bell's argument, on the other hand, depends on
assuming no causal influence either way, from aA to bB or from bB to
aA. The point is that all such causal information is isolated in the
common cause lambda, which is not omitted from the conditioning
statement.
Jayne's other objection is that it's possible lambda may have some
exogenous time dependence, so that calculating correlations by pooling
data from different runs of the experiment is erroneous. This is
technically possible, but would require quite an impressive conspiracy
in which the choices of the experimenter to start runs when he did are
somehow mysteriously tuned to synchronize with the time dependence of
lambda in non-trivial ways.
Regarding your own comments:
Bell does not presuppose a frequentist definition of probability -- no
more than does any other statistical experiment. He makes certain
assumptions and then uses relative frequencies merely to calculate
probabilities given those assumptions.
Putting a philosophical sounding name on something, like
"counter-factual definiteness", can have the unfortunate effect of
making it sound more questionable than it really should be.
What precisely is naive about Bell's ideas of locality and realism?
Alfred Einstead
> Mark, hope you find this useful:
> Yes, Everett's formulation of the relative state metatheory is the
> same as many-worlds, but the language has evolved a lot from Everett's
> original article [2] and some of his work has been extended,
> especially in the area of decoherence. (See "What is decoherence?")
> This has confused some people into thinking that Everett's "relative
> state metatheory" and DeWitt's "many-worlds interpretation" are
> different theories.
I'm already familiar with the whole line of evolution and am, in
essence one step past that; particularly -- one step onto the point
of recognizing that much of the confusion is internal and rests
on the fact that nobody got around to actually explicating the
theretofore unresolved term "world".
To address that, you have to go back to basics. In Classical
theory, if the evolution law is deterministic (i.e., if the
equations form a well-posed Cauchy problem) a world is uniquely
determined by the setting of all coordinates and velocities --
that is: of all initial data (more generally: of all space-time
boundary data).
The space of all possible settings of boundary data comprises what
we call its "phase space".
The most general state in a classical system is a probability
distribution in this space. Such a distribution gives you
a mixture of possible settings to the boundary data and so
comprises a mixture of possible worlds. In fact, this is
acknowledged as such, by calling this mixture an "ensemble".
Ensembles are mixed states and are generally visualized as a
fuzzy sort of thing consisting of a continuous smearing of
possible worlds clustered around a central point.
At the extreme case is the singular distribution: the delta
function, where the distribution is concentrated on one point
alone. This setting, as described above, uniquely defines a
single world and so corresponds to a "world". The singular
distributions are pure states.
So, the corresponding generalizations are:
world = pure state
multi-world = ensemble = mixed state.
A pure state is a world, and a world is a pure state. One
could even go as far as to say that the terms "state" and
"world" are really synonymous. And so the problem of
explicating the term "world" is thus resolved, and any
confusion regarding issues relating to it, eliminated.
> Everett tended to speak in terms of the measuring apparatus being
> split by the measurement, into non-interfering states, without
> presenting a detailed analysis of *why* a measuring apparatus was so
> effective at destroying interference effects after a measurement,
This phenomenon is known as superselection.
See my 3 articles under the "some questions on decoherence and QM"
thread where the general issue is dealt with in depth and resolved.
Daniel Davis
> > conflict with experiment. Since Bell's inequality presupposes some very
There is a conflict between:
1) Some assumption Bell uses to produce his inequality.
2) The assumptions used in interpreting the results of the experiment.
3) The results of the experiment.
It may be that "there is a hidden variable theory to explain this" is
the faulty assumption. Maybe not. But given the lack of a particularly
cogent alternative, and the conceptual confusion that seems to
surround this issue, I personally am not so quick to jump to
conclusions.
> Jaynes has many incisive things to say about the role of probability
> in physics; however, I believe he has uncharacteristically fumbled the
> ball in regard to the issue of Bell inequalities. His first basic
> objection is that Bell's assumption
>
> P(A|a,b,lambda) = P(A|a,lambda)
That isn't his objection. His objection is to:
P(AB|abL) = P(A|aL)P(B|bL)
The correct factorization is
P(AB|abL) = P(A|BabL)P(B|abL)
I think Jaynes grants that P(B|abL) = P(B|bL). He seems to be
objecting to
P(A|BabL) = P(A|aL).
> ... The point is that all such causal information is isolated in the
> common cause lambda, which is not omitted from the conditioning
> statement.
I do agree with that, though. I usually agree with Jaynes, but I don't
here. The point of the lambda construction is to create a hidden
variable theory - lambda is supposed to be able to make the results
for A,B conditionally independent, when conditioned on lambda.
Otherwise, what was the point of the hidden variable? What does a
hidden variable theory mean, if not that?
The construction of L, as a hidden variable that "predetermines the
results of all measurements on A", should allow P(A|BabL) = P(A|aL).
Actually, as we can see, even here L doesn't determine the outcome -
it is recognized that "a" is also relevant information.
In this vein, I may in fact agree with Jaynes after all. He later
states that he thinks Einstein would have liked time varying theories.
(Why not dependencies on spacetime intervals?). In such a case, you
have to be very careful that you have enough info in "aL", like
precise time intervals, to actually determine A - if you don't, then
"Bb" may carry additional info for predicting A, and so the
simplification P(A|BabL) = P(A|aL) will in fact be incorrect. Seen in
this way, I can agree with Jaynes.
> Jayne's other objection is that it's possible lambda may have some
> exogenous time dependence, so that calculating correlations by pooling
> data from different runs of the experiment is erroneous. This is
> technically possible, but would require quite an impressive conspiracy
> in which the choices of the experimenter to start runs when he did are
> somehow mysteriously tuned to synchronize with the time dependence of
> lambda in non-trivial ways.
How so? Can you show that Bell's derivation still holds when arbitrary
spacetime functions are part of the hidden variable theory? Has
anyone?
############
As an aside, how could you ever disprove that a supposed "random"
event in fact deterministically depended on a hidden variable, but
that dependency was subject to oscillation in spacetime much finer
than your ability to measure?
Like -
Result = (lambda + delta_spacetime*omega) MOD 2pi
I can always hypothesize that omega
omega*experimental_resolution_spacetime >> 2pi
So, it looks random with current means of measurement, but is
determined.
Since I think you can always do that, it ordinarily doesn't make for
much of a theory. But if it is a choice between the conceptual muddle
of quantum theory interpretations on the one hand, and such a
spacetime hidden variable theory and tidy determinism on the other
hand, the latter starts looking pretty good.
Buy Buy -- Dan Davis
Eric Dennis
> ede...@princeton.edu (Eric Dennis) wrote:
> > Jaynes has many incisive things to say about the role of probability
> > in physics; however, I believe he has uncharacteristically fumbled the
> > ball in regard to the issue of Bell inequalities. His first basic
> > objection is that Bell's assumption
> >
> > P(A|a,b,lambda) = P(A|a,lambda)
> That isn't his objection. His objection is to:
>
> P(AB|abL) = P(A|aL)P(B|bL)
>
> The correct factorization is
>
> P(AB|abL) = P(A|BabL)P(B|abL)
>
> I think Jaynes grants that P(B|abL) = P(B|bL). He seems to be
> objecting to
> P(A|BabL) = P(A|aL).
In his critical quotation of Bell after equation (15), it does seem
Jaynes is objecting to P(B|abL) = P(B|bL) as well. He's not explicit
on this point, but I agree the urn example is more relevant to the
case of omitting the measurement result from the conditioning
statement.
> In this vein, I may in fact agree with Jaynes after all. He later
> states that he thinks Einstein would have liked time varying theories.
> (Why not dependencies on spacetime intervals?). In such a case, you
> have to be very careful that you have enough info in "aL", like
> precise time intervals, to actually determine A - if you don't, then
> "Bb" may carry additional info for predicting A, and so the
> simplification P(A|BabL) = P(A|aL) will in fact be incorrect. Seen in
> this way, I can agree with Jaynes.
If the idea is that the hidden variables are still local but happen to
be acting at (t_A,x_A) differently than at (t_B,x_B) in just the right
way -- not through any physical influence, mind you -- to produce
these correlations, the problem is that (t_A,x_A) and (t_B,x_B) are
chosen arbitrarily (within constraints) by the experimenter.
Jaynes' objection here is similar to the objection from determinism:
that all these measured correlations result from pre-existing
correlations between the two polarizers (etc.) you happened to pull
off the shelf last week when you were setting up the experiment. Again
these seemingly random choices of the experimenter (and the polarizer
manufacturers etc.) are conspiring to give the appearance of
non-locality!
> How so? Can you show that Bell's derivation still holds when arbitrary
> spacetime functions are part of the hidden variable theory? Has
> anyone?
No. If you are allowed to tune the spacetime functions just right, you
can indeed get the correlations.
> As an aside, how could you ever disprove that a supposed "random"
> event in fact deterministically depended on a hidden variable, but
> that dependency was subject to oscillation in spacetime much finer
> than your ability to measure? [...]
This is correct. It's just that the dependencies need to be
conspiratorial, given the freedom of the experimenter. Note that these
dependencies may just as well be probablistic as deterministic -- that
is a completely distinct issue. The issue here is not determinism but
locality.
Daniel Davis
ede...@princeton.edu (Eric Dennis) wrote in message news:<ef463682.0301...@posting.google.com>...
> buybuyd...@yahoo.com (Daniel Davis) wrote:
>
> > I think Jaynes grants that P(B|abL) = P(B|bL). He seems to be
> > objecting to
> > P(A|BabL) = P(A|aL).
>
> In his critical quotation of Bell after equation (15), it does seem
> Jaynes is objecting to P(B|abL) = P(B|bL) as well. He's not explicit
> on this point, but I agree the urn example is more relevant to the
> case of omitting the measurement result from the conditioning
> statement.
I don't think so. See Jaynes next paragraph:
####
Note, however, that merely knowing the direction of the A measurement
does not change any predictions at B [ed. P(B|abL) = P(B|bL) ]...
As we would expect from (15), it is necessary to know also the result
of the A measurement before the correlation effects our predictions.
[ ed. P(B|abL) = P(B|AbL) = P(B|bL) <> P(B|AabL) ]
####
You need to know both (a,A) to know anything more about B; either
alone tells you nothing more.
> If the idea is that the hidden variables are still local but happen to
> be acting at (t_A,x_A) differently than at (t_B,x_B) in just the right
> way -- not through any physical influence, mind you -- to produce
> these correlations, the problem is that (t_A,x_A) and (t_B,x_B) are
> chosen arbitrarily (within constraints) by the experimenter.
But the values the experimenter can get at those randomly chosen
values are determined by the initial conditions L and the values (t,x)
chosen.
> Jaynes' objection here is similar to the objection from determinism:
It should be: I read Jaynes as a determinist. Randomness = inability
to predict, not "the universe can't decide what it wants to be".
Epistemological randomness, not ontological randomness.
> that all these measured correlations result from pre-existing
> correlations between the two polarizers (etc.) you happened to pull
> off the shelf last week when you were setting up the experiment.
No - the correlations result from the hidden variable L and the
specifics of how , when, and where you measure.
> Again
> these seemingly random choices of the experimenter (and the polarizer
> manufacturers etc.) are conspiring to give the appearance of
> non-locality!
I assume that you don't find it strange that experimental measurements
depend on
the specifics of how you take the measurements.
You say that the results are conspiring to give the appearance of
nonlocality. They may "appear" to violate non-locality to you, but
that is an interpretation of the experimental results. Perhaps the
interpretation is in error.
> > How so? Can you show that Bell's derivation still holds when arbitrary
> > spacetime functions are part of the hidden variable theory? Has
> > anyone?
>
> No. If you are allowed to tune the spacetime functions just right, you
> can indeed get the correlations.
Could you demonstrate?
Why wouldn't that be just the hidden variable theory that Bell claims
cannot exist?
> > As an aside, how could you ever disprove that a supposed "random"
> > event in fact deterministically depended on a hidden variable, but
> > that dependency was subject to oscillation in spacetime much finer
> > than your ability to measure? [...]
>
> This is correct.
Ok. It seems to me you have granted my first objection to Bell - the
claim that Bell has proven that there can't be a hidden variable
theory that accounts for QM measurements is false.
> It's just that the dependencies need to be
> conspiratorial, given the freedom of the experimenter. Note that these
> dependencies may just as well be probablistic as deterministic -- that
> is a completely distinct issue. The issue here is not determinism but
> locality.
The conspiring language leads me to believe that Jaynes objections
that Bell has confused conditional probabilities with causation are
possibly on the mark.
Consider a problem. I put a red ball and a white ball in a bag.
Without looking, I pull one ball out and put it in an identical bag. I
send one bag to NY, and one to LA. A month later, when I open the bag
in LA, I know what is in the bag in NY instantaneously.
Has the measurement at LA "conspired" with the measurement in NY? Has
locality been violated? I don't think so. If one wanted to be
tediously QM, we could have the ball picking determined in the same
way as for Schroedingers cat. One could claim an instantaneous
collapse of the wave functions for the balls. What has collapsed is
our *ignorance* about which ball is where.
The instantaneous change in our state of knowledge about a distant
event is confused with an instantaneous transfer of energy/information
to that distant location. The collapse of a probability function is
interpreted as a physical collapse instead of a collapse of our
ignorance.
####
I'd like to discuss this further. I think I have a pretty good handle
on Jaynes and how he thinks. I should explain that I am not a
physicist, and that while I once upon a time too a QM class, I don't
remember a heck of a lot. I got my phd in electrical engineering, with
my main interests in machine learning and probabilistic inference.
I can represent Jayne's side of the argument, and the theory of
probabilistic inference he would favor. If you can take Bell's side,
and handle the physics, we can at least work out where the precise
points where we disagree. Maybe I'll find I disagree with Jaynes after
all.
####
Maybe you could explain something in Jaynes to me. He says:
"The spooky business appears in the joint probabiliy, which QM gives
as P(AB|ab)=0.5(sin(theta/2))^2, where cos(theta)=a*b." (dot product
of a and b)
Regardless of Bell's inequality gymnastics, if a hidden variable
theory could produce that joint distribution, then Bell would be shown
to be wrong, correct?
When Jaynes says, "QM gives", what does he mean? Where does this
equation come from?
####
Do you have a favorite form of Bell's Inequalities, experimental
results and interpretations that you feel you understand well enough
to explain and defend?
I've followed a web page on Bell's derivation a fair way through, but
find it tedious going.
http://www.mtnmath.com/whatth/node61.html
I've been unable to justify certain steps of the derivation. I also
don't really have the experimental data resulting from the experiment.
michaelprice
>
> Putting a philosophical sounding name on something, like
> "counter-factual definiteness", can have the unfortunate effect of
> making it sound more questionable than it really should be.
I entirely agree. A common practicem unfortunately.
> What precisely is naive about Bell's ideas of locality and realism?
Here's something I wrote awhile back about Bell, locality, realism
and "counter-factual definiteness". You may find it useful, whether
or not you agree with many-worlds, which is the context within
which it was written: http://www.hedweb.com/manworld.htm
Q32
Does the EPR experiment prohibit locality?
What about Bell's Inequality?
The EPR experiment is widely regarded as the definitive gedanken experiment
for demonstrating that quantum mechanics is non-local (requires
faster-than-light communication) or incomplete. We shall see that it implies
neither.
The EPR experiment was devised, in 1935, by Einstein, Podolsky and Rosen to
demonstrate that quantum mechanics was incomplete [E]. Bell, in 1964,
demonstrated that any hidden variables theory, to replicate the predictions
of QM, must be non-local [B]. QM predicts strong correlations between
separated systems, stronger than any local hidden variables theory can
offer. Bell encoded this statistical prediction in the form of some famous
inequalities that apply to any type of EPR experiment. Eberhard, in the late
1970s, extended Bell's inequalities to cover any local theory, with or
without hidden variables. Thus the EPR experiment plays a central role in
sorting and testing variants of QM. All the experiments attempting to test
EPR/Bell's inequality to date (including Aspect's in the 1980s [As]) are in
line with the predictions of standard QM - hidden variables are ruled out.
Here is the paradox of the EPR experiment. It seems to imply that any
physical theory must involve faster-than-light "things" going on to maintain
these "spooky" action-at-a-distance correlations and yet still be compatible
with relativity, which seems to forbid FTL.
Let's examine the EPR experiment in more detail.
So what did EPR propose? The original proposal was formulated in terms of
correlations between the positions and momenta of two once-coupled
particles. Here I shall describe it in terms of the spin (a type of angular
momentum intrinsic to the particle) of two electrons. [In this treatment I
shall ignore the fact that electrons always form antisymmetric combinations.
This does not alter the results but does simplify the maths.] Two initially
coupled electrons, with opposed spins that sum to zero, move apart from each
other across a distance of perhaps many light years, before being separately
detected, say, by me on Earth and you on Alpha Centauri with our respective
measuring apparatuses. The EPR paradox results from noting that if we choose
the same (parallel) spin axes to measure along then we will observe the two
electrons' spins to be anti-parallel (i.e. when we communicate we find that
the spin on our electrons are correlated and opposed). However if we choose
measurement spin axes that are perpendicular to each other then there is no
correlation between electron spins. Last minute alterations in a detector's
alignment can create or destroy correlations across great distances. This
implies, according to some theorists, that faster-than-light influences
maintain correlations between separated systems in some circumstances and
not others.
Now let's see how many-worlds escapes from this dilemma.
The initial state of the wavefunction of you, me and the electrons and the
rest of the universe may be written:
|psi> = |me> |electrons> |you> |rest of universe>
on in on
Earth deep Alpha
space Centauri
or more compactly, ignoring the rest of the universe, as:
|psi> = |me, electrons, you>
And
|me> represents me on Earth with my detection apparatus.
|electrons> = (|+,-> - |-,+>)/sqrt(2)
represents a pair electrons, with the first electron travelling
towards Earth and the second electron travelling towards Alpha
Centauri.
|+> represents an electron with spin in the +z direction
|-> represents an electron with spin in the -z direction
It is an empirically established fact, which we just have to accept, that we
can relate spin states in one direction to spin states in other directions
like so (where "i" is the sqrt(-1)):
|left> = (|+> - |->)/sqrt(2)(electron with spin in -x direction)
|right> = (|+> + |->)/sqrt(2)(electron with spin in +x direction)
|up>= (|+> + |->i)/sqrt(2) (electron with spin in +y direction)
|down> = (|+> - |->i)/sqrt(2) (electron with spin in -y direction)
and inverting:
|+> = (|right> + |left>)/sqrt(2) = (|up> + |down>)/sqrt(2)
|-> = (|right> - |left>)/sqrt(2) = (|down> - |up>)i/sqrt(2)
(In fancy jargon we say that the spin operators in different directions form
non-commuting observables. I shall eschew such obfuscations.)
Working through the algebra we find that for pairs of electrons:
|+,-> - |-,+> = |left,right> - |right,left>
= |up,down>i- |down,up>
I shall assume that we are capable of either measuring spin in the x or y
direction, which are both perpendicular the line of flight of the electrons.
After having measured the state of the electron my state is described as one
of either:
|me[l]> represents me + apparatus + records having measured
and recorded the x-axis spin as "left"
|me[r]> ditto with the x-axis spin as "right"
|me[u]> ditto with the y-axis spin as "up"
|me[d]> ditto with the y-axis spin as "down"
Similarly for |you> on Alpha Centauri. Notice that it is irrelevant how we
have measured the electron's spin. The details of the measurement process
are irrelevant. (See "What is a measurement?" if you're not convinced.) To
model the process it is sufficient to assume that there is a way, which we
have further assumed does not disturb the electron. (The latter assumption
may be relaxed without altering the results.)
To establish familiarity with the notation let's take the state of the
initial wavefunction as:
|psi>_1 = |me,left,up,you>
/ \
/ \
first electron in left second electron in up state
state heading towards heading towards you on
me on EarthAlpha Centauri
After the electrons arrive at their detectors, I measure the spin along the
x-axis and you along the y-axis. The wavefunction evolves into |psi>_2:
local
|psi>_1 ============> |psi>_2 = |me[l],left,up,you[u]>
observation
which represents me having recorded my electron on Earth with spin left and
you having recorded your electron on Alpha Centauri with spin up. The index
in []s indicates the value of the record. This may be held in the observer's
memory, notebooks or elsewhere in the local environment (not necessarily in
a readable form). If we communicate our readings to each other the
wavefunctions evolves into |psi>_3:
remote
|psi>_2 ============> |psi>_3 = |me[l,u],left,up,you[u,l]>
communication
where the second index in []s represents the remote reading communicated to
the other observer and being recorded locally. Notice that the results both
agree with each other, in the sense that my record of your result agrees
with your record of your result. And vice versa. Our records are consistent.
That's the notation established. Now let's see what happens in the more
general case where, again,:
|electrons> = (|+,-> - |-,+>)/sqrt(2).
First we'll consider the case where you and I have previously arranged to
measure the our respective electron spins along the same x-axis.
Initially the wavefunction of the system of electrons and two experimenters
is:
|psi>_1
= |me,electrons,you>
= |me>(|left,right> - |right,left>)|you> /sqrt(2)
= |me,left,right,you> /sqrt(2)
- |me,right,left,you> /sqrt(2)
Neither you or I are yet unambiguously split.
Suppose I perform my measurement first (in some time frame). We get
|psi>_2
= (|me[l],left,right> - |me[r],right,left>)|you> /sqrt(2)
= |me[l],left,right,you> /sqrt(2)
- |me[r],right,left,you> /sqrt(2)
My measurement has split me, although you, having made no measurement,
remain unsplit. In the full expansion the terms that correspond to you are
identical.
After the we each have performed our measurements we get:
|psi>_3
= |me[l],left,right,you[r]> /sqrt(2)
- |me[r],right,left,you[l]> /sqrt(2)
The observers (you and me) have been split (on Earth and Alpha Centauri)
into relative states (or local worlds) which correlate with the state of the
electron. If we now communicate over interstellar modem (this will take a
few years since you and I are separated by light years, but no matter). We
get:
|psi>_4
= |me[l,r],left,right,you[r,l]> /sqrt(2)
- |me[r,l],right,left,you[l,r]> /sqrt(2)
The world corresponding to the 2nd term in the above expansion, for example,
contains me having seen my electron with spin right and knowing that you
have seen your electron with spin left. So we jointly agree, in both worlds,
that spin has been conserved.
Now suppose that we had prearranged to measure the spins along different
axes. Suppose I measure the x-direction spin and you the y-direction spin.
Things get a bit more complex. To analyse what happens we need to decompose
the two electrons along their respective spin axes.
|psi>_1 =
|me,electrons,you>
= |me>(|+,-> - |-,+>)|you>/sqrt(2)
= |me> (
(|right>+|left>)i(|down>-|up>)
- (|right>-|left>)(|down>+|up>)
) |you> /2*sqrt(2)
= |me> (
|right>(|down>-|up>)i
+ |left> (|down>-|up>)i
- |right>(|down>+|up>)
+ |left> (|down>+|up>)
) |you> /2*sqrt(2)
= |me> (
|right,down> (i-1) - |right,up> (1+i)
+ |left,up> (1-i)+ |left,down> (1+i)
) |you> /2*sqrt(2)
= (
+ |me,right,down,you> (i-1)
- |me,right,up,you> (i+1)
+ |me,left,up,you>(1-i)
+ |me,left,down,you> (1+i)
) /2*sqrt(2)
So after you and I make our local observations we get:
|psi>_2 =
(
+ |me[r],right,down,you[d]> (i-1)
- |me[r],right,up,you[u]> (i+1)
+ |me[l],left,up,you[u]>(1-i)
+ |me[l],left,down,you[d]> (1+i)
) /2*sqrt(2)
Each term realises a possible outcome of the joint measurements. The
interesting thing is that whilst we can decompose it into four terms there
are only two states for each observer. Looking at myself, for instance, we
can rewrite this in terms of states relative to *my* records/memories.
|psi>_2 =
(
|me[r],right> ( |down,you[d]> (i-1) - |up,you[u]> (i+1) )
+ |me[l],left> ( |up,you[u]> (1-i) + |down,you[d]> (1+i) )
) /2*sqrt(2)
And we see that there are only two copies of me. Equally we can rewrite the
expression in terms of states relative to your records/memory.
|psi>_2 =
(
( |me[l],left> (1-i) - |me[r],right> (i+1) ) |up,you[u]>
+ ( |me[r],right> (i-1) + |me[l],left> (1+i) ) |down,you[d]>
) /2*sqrt(2)
And see that there are only two copies of you. We have each been split into
two copies, each perceiving a different outcome for our electron's spin, but
we have not been split by the measurement of the remote electron's spin.
After you and I communicate our readings to each other, more than four years
later, we get:
|psi>_3 =
(
+ |me[r,d],right,down,you[d,r]> (i-1)
- |me[r,u],right,up,you[u,r]> (i+1)
+ |me[l,u],left,up,you[u,l]>(1-i)
+ |me[l,d],left,down,you[d,l]> (1+i)
) /2*sqrt(2)
The decomposition into four worlds is forced and unambiguous after
communication with the remote system. Until the two observers communicated
their results to each other they were each unsplit by each others'
measurements, although their own local measurements had split themselves.
The splitting is a local process that is causally transmitted from system to
system at light or sub-light speeds. (This is a point that Everett stressed
about Einstein's remark about the observations of a mouse, in the Copenhagen
interpretation, collapsing the wavefunction of the universe. Everett
observed that it is the mouse that's split by its observation of the rest of
the universe. The rest of the universe is unaffected and unsplit.)
When all communication is complete the worlds have finally decomposed or
decohered from each other. Each world contains a consistent set of
observers, records and electrons, in perfect agreement with the predictions
of standard QM. Further observations of the electrons will agree with the
earlier ones and so each observer, in each world, can henceforth regard the
electron's wavefunction as having collapsed to match the historically
recorded, locally observed values. This justifies our operational adoption
of the collapse of the wavefunction upon measurement, without having to
strain our credibility by believing that it actually happens.
To recap. Many-worlds is local and deterministic. Local measurements split
local systems (including observers) in a subjectively random fashion;
distant systems are only split when the causally transmitted effects of the
local interactions reach them. We have not assumed any non-local FTL
effects, yet we have reproduced the standard predictions of QM.
So where did Bell and Eberhard go wrong? They thought that all theories that
reproduced the standard predictions must be non-local. It has been pointed
out by both Albert [A] and Cramer [C] (who both support different
interpretations of QM) that Bell and Eberhard had implicity assumed that
every possible measurement - even if not performed - would have yielded a
single definite result. This assumption is called contra-factual
definiteness or CFD [S]. What Bell and Eberhard really proved was that every
quantum theory must either violate locality or CFD. Many-worlds with its
multiplicity of results in different worlds violates CFD, of course, and
thus can be local.
Thus many-worlds is the only local quantum theory in accord with the
standard predictions of QM and, so far, with experiment.
[A] David Z Albert, Bohm's Alternative to Quantum Mechanics Scientific
American (May 1994)
[As] Alain Aspect, J Dalibard, G Roger Experimental test of Bell's
inequalities using time-varying analyzers Physical Review Letters Vol 49 #25
1804 (1982).
[C] John G Cramer The transactional interpretation of quantum mechanics
Reviews of Modern Physics Vol 58 #3 647-687 (1986)
[B] John S Bell: On the Einstein Podolsky Rosen paradox Physics 1 #3 195-200
(1964).
[E] Albert Einstein, Boris Podolsky, Nathan Rosen: Can quantum-mechanical
description of physical reality be considered complete? Physical Review Vol
41 777-780 (15 May 1935).
[S] Henry P Stapp S-matrix interpretation of quantum-theory Physical Review
D Vol 3 #6 1303 (1971)
Ralph Hartley
>>common cause lambda, which is not omitted from the conditioning
>>statement.
>
> I do agree with that, though. I usually agree with Jaynes, but I don't
> here. The point of the lambda construction is to create a hidden
> variable theory - lambda is supposed to be able to make the results
> for A,B conditionally independent, when conditioned on lambda.
> Otherwise, what was the point of the hidden variable? What does a
> hidden variable theory mean, if not that?
>
> The construction of L, as a hidden variable that "predetermines the
> results of all measurements on A", should allow P(A|BabL) = P(A|aL).
> Actually, as we can see, even here L doesn't determine the outcome -
> it is recognized that "a" is also relevant information.
>
> In this vein, I may in fact agree with Jaynes after all. He later
> states that he thinks Einstein would have liked time varying theories.
> (Why not dependencies on spacetime intervals?). In such a case, you
> have to be very careful that you have enough info in "aL", like
> precise time intervals, to actually determine A - if you don't, then
> "Bb" may carry additional info for predicting A, and so the
> simplification P(A|BabL) = P(A|aL) will in fact be incorrect. Seen in
> this way, I can agree with Jaynes.
But any information avilable at both measurements is part of L, by
definition. "Bb" is information local to the second measurement but NOT the
first. Sure, the exact timing of the second measurement could be correlated
with the outcome of the first, but unless that were part of L, that would
violate locality.
> As an aside, how could you ever disprove that a supposed "random"
> event in fact deterministically depended on a hidden variable, but
> that dependency was subject to oscillation in spacetime much finer
> than your ability to measure?
> So, it looks random with current means of measurement, but is
> determined.
But the violation of Bell's inequality is a matter of things looking too
deterministic, not too random.
It is possible in principle that the "arbitrary" choices "a" and "b" could
be determined (from L) in just the right way to give the correlations, but
since "a" and "b" can be produced by an arbitrary mechanism (which the
experimenter chooses) this would reqire an increadible conspiracy. The laws
of phisics would have to "reverse engineer" the experimental set up. For
instance, the addition of a "not" gate to the mechanism for choosing the
measurement at one of the detectors, would have to have the same effect at
distant points, regardless of how it was implemented.
Ralph Hartley
Tim S
>
> ede...@princeton.edu (Eric Dennis) wrote in message
> news:<ef463682.0301...@posting.google.com>...
>> buybuyd...@yahoo.com (Daniel Davis) wrote:
<Jaynes' and hidden-variable interpretations>
>> If the idea is that the hidden variables are still local but happen to
>> be acting at (t_A,x_A) differently than at (t_B,x_B) in just the right
>> way -- not through any physical influence, mind you -- to produce
>> these correlations, the problem is that (t_A,x_A) and (t_B,x_B) are
>> chosen arbitrarily (within constraints) by the experimenter.
>
> But the values the experimenter can get at those randomly chosen
> values are determined by the initial conditions L and the values (t,x)
> chosen.
>
>> Jaynes' objection here is similar to the objection from determinism:
>
> It should be: I read Jaynes as a determinist. Randomness = inability
> to predict, not "the universe can't decide what it wants to be".
> Epistemological randomness, not ontological randomness.
>
>> that all these measured correlations result from pre-existing
>> correlations between the two polarizers (etc.) you happened to pull
>> off the shelf last week when you were setting up the experiment.
>
> No - the correlations result from the hidden variable L and the
> specifics of how , when, and where you measure.
This can't be true if Jaynes' argument is to work against Bell's Theorem.
>
>> Again
>> these seemingly random choices of the experimenter (and the polarizer
>> manufacturers etc.) are conspiring to give the appearance of
>> non-locality!
>
> I assume that you don't find it strange that experimental measurements
> depend on
> the specifics of how you take the measurements.
Yes, but the results of independent experiments shouldn't be correlated.
>
> You say that the results are conspiring to give the appearance of
> nonlocality. They may "appear" to violate non-locality to you, but
> that is an interpretation of the experimental results. Perhaps the
> interpretation is in error.
>
>>> How so? Can you show that Bell's derivation still holds when arbitrary
>>> spacetime functions are part of the hidden variable theory? Has
>>> anyone?
>>
>> No. If you are allowed to tune the spacetime functions just right, you
>> can indeed get the correlations.
>
<snip>
>
>> It's just that the dependencies need to be
>> conspiratorial, given the freedom of the experimenter. Note that these
>> dependencies may just as well be probablistic as deterministic -- that
>> is a completely distinct issue. The issue here is not determinism but
>> locality.
>
> The conspiring language leads me to believe that Jaynes objections
> that Bell has confused conditional probabilities with causation are
> possibly on the mark.
I don't think you fully appreciate the depth of the conspiracy that's
required.
Well-known comparable examples from philosophy are:
a) The brain in a vat. A person's brain is kept in a vat of nutrients, with
its incoming and outgoing nerves hooked up to a giant computer. A malicious
technician manipulates the sensory inputs so that the brain hallucinates an
imaginary world unlike the real one.
b) The Cartesian demon. Descartes claimed that the world can't be _too_
different from what our senses and reasoning tell us, because a benificent
God wouldn't deceive us like that. By contrast, a Cartesian Demon is a
malicious being with supernatural powers who fools our senses or reasoning
to make us believe in a world quite different from the real one.
c) The claim by a few creationists that God created the world six thousand
years ago, but complete with sediment layers, fossils, etc carefully
constructed to make it _look_ as though the earth has four and a half
billion years of rationally reconstructable history.
Jaynes is effectively claiming that the real laws of physics _could_ be a
local hidden-variable theory, if the initial conditions had been maliciously
set up to make it look like quantum theory. The twist is that the initial
conditions would have to be specially tailored to the experiments we were
going to do. As with the second imaginary scenario above, it can only be set
up to fool some particular set of observers (i.e. us -- or the brain in the
vat, rather than the people who look after it).
The argument is logically impeccable -- the universe could indeed be
maliciously conspiring to bring about these experimental results -- but if
you're able to believe in that sort of conspiracy, you're able to believe
pretty much anything at all. Bell takes it for granted that nobody's going
to believe in something that bizarre. This isn't an oversight or a
confusion.
Tim
Ilja Schmelzer
> You say that the results are conspiring to give the appearance of
> nonlocality. They may "appear" to violate non-locality to you, but
> that is an interpretation of the experimental results. Perhaps the
> interpretation is in error.
But you need quite good arguments for this "perhaps".
> Ok. It seems to me you have granted my first objection to Bell - the
> claim that Bell has proven that there can't be a hidden variable
> theory that accounts for QM measurements is false.
Which was never Bell's claim. Instead, Bell has started from Bohmian
mechanics - a quite simple hidden variable theory - which has one
uncommon and unpopular property: non-locality (a need for a preferred
frame).
His aim was to prove that this particular feature is no accident but a
necessity for hidden variable theories. This essentially weakens the
objection "needs a preferred frame" against Bohmian mechanics.
>> It's just that the dependencies need to be conspiratorial, given
>> the freedom of the experimenter.
> The conspiring language leads me to believe that Jaynes objections
> that Bell has confused conditional probabilities with causation are
> possibly on the mark.
And it leads me to believe that Jaynes objections are off the mark.
> Consider a problem. I put a red ball and a white ball in a bag.
> Without looking, I pull one ball out and put it in an identical bag. I
> send one bag to NY, and one to LA. A month later, when I open the bag
> in LA, I know what is in the bag in NY instantaneously.
This gives an example of a correlation which does not violate Bell's
inequality. Whoever believes this is a valid objection against Bell
has not understood the point of Bell's theorem - which is that QM
correlations cannot be explained in such a simple way.
> Has the measurement at LA "conspired" with the measurement in NY?
No necessity to make such strange assumptions, because there is no
violation of Bell's inequalities.
> One could claim an instantaneous collapse of the wave functions for
> the balls. What has collapsed is our *ignorance* about which ball is
> where.
Of course, one could make a lot of other unjustified claims about
situations which have nothing to do with violations of Bell's
inequality.
> The instantaneous change in our state of knowledge about a distant
> event is confused with an instantaneous transfer of energy/information
> to that distant location.
Its you who is confused - you confuse a situation which can be easily
described with local hidden variables ("Bell theories") and where
Bell's inequality holds, without any chance to violate them, with a
situation where Bell's inequality is violated.
I recommend you to try to understand the seriousness of violations of
Bell's inequality from point of view of common sense. I hope
www.ilja-schmelzer.de/realism/game.html may be helpful.
> Regardless of Bell's inequality gymnastics, if a hidden variable
> theory could produce that joint distribution, then Bell would be shown
> to be wrong, correct?
A local one, yes. A simple (but nonlocal) hidden variable theory
which produces them was already well-known to Bell: Bohmian mechanics.
> When Jaynes says, "QM gives", what does he mean? Where does this
> equation come from?
That's indeed simple standard two-particle QM, but the main advantage
is that there is no much necessity for laymen to care about the QM
derivation: Nobody is questioning this part of the derivation,
moreover there are experimental results in support of the QM
prediction which show that the point is one about Nature against one
of the assumptions of local realism.
BTW, I see exactly no reason to give up realism. The violation
therefore simply proves the existence of faster than light causal
influences, that's all.
Oz
michaelprice <michae...@ntlworld.com> writes
>Q32
>Does the EPR experiment prohibit locality?
>What about Bell's Inequality?
>The EPR experiment is widely regarded as the definitive gedanken experiment
>for demonstrating that quantum mechanics is non-local (requires
>faster-than-light communication) or incomplete.
>We shall see that it implies
>neither.
OK.
>All the experiments attempting to test
>EPR/Bell's inequality to date (including Aspect's in the 1980s [As]) are in
>line with the predictions of standard QM - hidden variables are ruled out.
I'm not sure precisely what you mean by 'hidden variables'.
>Here is the paradox of the EPR experiment. It seems to imply that any
>physical theory must involve faster-than-light "things" going on to maintain
>these "spooky" action-at-a-distance correlations and yet still be compatible
>with relativity, which seems to forbid FTL.
OK.
>The EPR paradox results from noting that if we choose
>the same (parallel) spin axes to measure along then we will observe the two
>electrons' spins to be anti-parallel (i.e. when we communicate we find that
>the spin on our electrons are correlated and opposed). However if we choose
>measurement spin axes that are perpendicular to each other then there is no
>correlation between electron spins.
OK. Hmm. I need to think on that.
I assume that the initial entangled pair have antiparallel spins.
So if I measure both along the same axis, they must be opposite.
If I measure with perpendicular axes I obtain no information on their
relative spins in the 'parallel' direction so I 'lose' the information
encoded in their antiparallelism and so there is no correlation.
OK, that looks good.
>Last minute alterations in a detector's
>alignment can create or destroy correlations across great distances. This
>implies, according to some theorists, that faster-than-light influences
>maintain correlations between separated systems in some circumstances and
>not others.
Hmmm. I have my doubts about this.
Since you cannot choose which polarisation you will get, all you need is
to describe the entangled pair as ONE particle which can only become two
if the two have opposite polarisation. FTL 'communication' may well not
apply to operations 'inside' a particle. After all, no paradoxes arise.
>The decomposition into four worlds is forced and unambiguous after
>communication with the remote system. Until the two observers communicated
>their results to each other they were each unsplit by each others'
>measurements, although their own local measurements had split themselves.
>The splitting is a local process that is causally transmitted from system to
>system at light or sub-light speeds. (This is a point that Everett stressed
>about Einstein's remark about the observations of a mouse, in the Copenhagen
>interpretation, collapsing the wavefunction of the universe. Everett
>observed that it is the mouse that's split by its observation of the rest of
>the universe. The rest of the universe is unaffected and unsplit.)
OK. This assumes that the particle cannot communicate 'internally' at
FTL speeds. What if it can? As far as I can see there are no paradoxes
with this view, whilst there is a de-facto paradox in 'many worlds'.
>Thus many-worlds is the only local quantum theory in accord with the
>standard predictions of QM and, so far, with experiment.
I can't agree, unless you come up with a better argument.
Daniel Davis
reiterate a couple of questions I had.
1)
Jaynes states that it is easy to verify the following:
P(A|a) = 1/2
P(B|b) = 1/2
but
P(AB|ab) = 0.5 (sin(theta/2))^2 where cos(theta)=a*b
Can someone point me to derivations of these?
2)
Regardless of Bell's inequality gymnastics, if a hidden variable
theory could produce that joint distribution, then Bell would be shown
to be wrong, correct?
Buy Buy -- Dan Davis
Ilja Schmelzer
> All the experiments attempting to test
> EPR/Bell's inequality to date (including Aspect's in the 1980s [As]) are in
> line with the predictions of standard QM - hidden variables are ruled out.
A "local" forgotten - Bohmian mechanics is not ruled out.
> Here is the paradox of the EPR experiment. It seems to imply that any
> physical theory must involve faster-than-light "things" going on to maintain
> these "spooky" action-at-a-distance correlations and yet still be compatible
> with relativity, which seems to forbid FTL.
But only seems. Going back to a good old Lorentz ether (a preferred
frame) defines a simple possibility to introduce FTL. This preferred
frame is hidden from observation? Indeed, it is. So what? Are
hidden variables forbidden in a hidden variable theory?
Thus, no paradox but only a conflict with a particular metaphysical
prejudice against a special example of a hidden variable - the
preferred frame of the Lorentz ether.
> Now let's see how many-worlds escapes from this dilemma.
As it can be seen, many-worlds escapes by talking a lot of words,
especially about splittings of universes.
Is this really an explanation? I propose the "FTL phone" test to this
"explanation". The basic idea is the following: Assume we have found
or created a device which works like an FTL phone. So you can use it
to talk with a Mars station without any delay for the speed of light.
It is reasonable that in this case Einstein causality should be
rejected. And that any "explanation" of this phone which preserves
Einstein causality is simply nonsense, and not an explanation. Now,
given some "explanation" of EPR experiments, we can try to use a
similar "explanation" for the FTL phone. If this replacement works,
the "explanation" should be rejected as nonsensical.
Note that the "FTL phone" is designed as a tool to reject _some_
claimed explanations of violations of Bell's inequality. It does not
handle them all. Especially it does not handle explicit rejections of
causality as well as general rejections of implicit observations.
But for many worlds the FTL phone is usually sufficient. Let's try:
> The initial state of the wavefunction of you, me and the electrons and the
> rest of the universe may be written:
>
> |psi> = |me> |electrons> |you> |rest of universe>
> on in on
> Earth deep Alpha
> space Centauri
> or more compactly, ignoring the rest of the universe, as:
> |psi> = |me, electrons, you>
> And
> |me> represents me on Earth with my detection apparatus.
> |electrons> = (|+,-> - |-,+>)/sqrt(2)
> represents a pair electrons, with the first electron travelling
> towards Earth and the second electron travelling towards Alpha
> Centauri.
>
> |+> represents an electron with spin in the +z direction
> |-> represents an electron with spin in the -z direction
Not much necessity to change anything. Maybe replacing "electron"
with "FTL-phone".
> It is an empirically established fact, which we just have to accept, that we
Hm, it seems that we can already stop here. An "explanation"
containing such a phrase is not an explanation. This seems obvious,
independent on our FTL phone argumentation. But, of course, we can
give an FTL phone explanation in a simple way:
"It is an empirically established fact, which we just have to accept,
that the FTL phone works."
And, of course, we can hide this by replacing "the FTL phone works" by
any equivalent phrase and then proving on several pages of text
the equivalence.
Nonetheless, let's continue. Last not least, this "explanation"
contains some other elements typical for "many world explanations" of
Bell.
> After having measured the state of the electron my state is described as one
> of either:
>
> |me[l]> represents me + apparatus + records having measured
> and recorded the x-axis spin as "left"
|me[A,B]> represents me + phone + records having said "A" and having heard "B"
> |me[r]> ditto with the x-axis spin as "right"
> |me[u]> ditto with the y-axis spin as "up"
> |me[d]> ditto with the y-axis spin as "down"
|me[A,notB]> ditto with "A" and having heard "not B"
|me[notA,B]> ditto with "not A" and having heard "B"
|me[notA,notB]> ditto with "not A" and having heard "not B"
> Similarly for |you> on Alpha Centauri. Notice that it is irrelevant how we
> have measured the electron's spin. The details of the measurement process
> are irrelevant.
> To establish familiarity with the notation let's take the state of the
> initial wavefunction as:
>
> |psi>_1 = |me,left,up,you>
|psi>_1 = |me,A,B,you>
> / \
> / \
> first electron in left second electron in up state
> state heading towards heading towards you on
> me on EarthAlpha Centauri
> After the electrons arrive at their detectors, I measure the spin along the
> x-axis and you along the y-axis.
I say A and you say "not B".
> The wavefunction evolves into |psi>_2:
>
> local
> |psi>_1 ============> |psi>_2 = |me[l],left,up,you[u]>
|psi>_1 ============> |psi>_2 = |me[AB],A,B,you[A,notB]>
> which represents me having recorded my electron on Earth with spin left and
> you having recorded your electron on Alpha Centauri with spin up. The index
> in []s indicates the value of the record. This may be held in the observer's
> memory, notebooks or elsewhere in the local environment (not necessarily in
> a readable form). If we communicate our readings to each other the
> wavefunctions evolves into |psi>_3:
>
> remote
> |psi>_2 ============> |psi>_3 = |me[l,u],left,up,you[u,l]>
> communication
|psi>_2 ============> |psi>_3 = 0
This happens as the result of "superposition", which has to be taken
as an "empirically established fact".
Of course, we can also support the FTL-phone explanation with
formulas. Especially we take them from some causal realistic
FTL-violating theory - the analogon of Bohmian mechanics. This theory
depends, as Bohmian mechanics, from a preferred time T.
Then we add some mystery language and deny the reality of the "wave
function" T which is only a mathematical tool to compute observable
probabilities but has no reality.
> And see that there are only two copies of you. We have each been split into
> two copies, each perceiving a different outcome for our electron's spin, but
> we have not been split by the measurement of the remote electron's spin.
Each of us has been split into two copies, hearing "A" vs. "not A"
(similarly "B" vs. "not B") on our local phone. But we have not been
split by the other guy saying something.
> After you and I communicate our readings to each other, more than four years
> later, we get:
>
> |psi>_3 =
> (
> + |me[r,d],right,down,you[d,r]> (i-1)
> - |me[r,u],right,up,you[u,r]> (i+1)
> + |me[l,u],left,up,you[u,l]>(1-i)
> + |me[l,d],left,down,you[d,l]> (1+i)
> ) /2*sqrt(2)
> The decomposition into four worlds is forced and unambiguous after
> communication with the remote system.
The same for the FTL phone. "Superposition" excludes here the
contradicting outcomes.
> Until the two observers communicated
> their results to each other they were each unsplit by each others'
> measurements, although their own local measurements had split themselves.
> The splitting is a local process that is causally transmitted from system to
> system at light or sub-light speeds. (This is a point that Everett stressed
> about Einstein's remark about the observations of a mouse, in the Copenhagen
> interpretation, collapsing the wavefunction of the universe. Everett
> observed that it is the mouse that's split by its observation of the rest of
> the universe. The rest of the universe is unaffected and unsplit.)
This consideration can be taken as it is.
> To recap. Many-worlds is local and deterministic. Local measurements split
> local systems (including observers) in a subjectively random fashion;
> distant systems are only split when the causally transmitted effects of the
> local interactions reach them. We have not assumed any non-local FTL
> effects, yet we have reproduced the standard predictions of QM.
The same for our explanation of the FTL phone.
> So where did Bell and Eberhard go wrong?
Nowhere. The explanation is not an explanation.
> They thought that all theories that
> reproduced the standard predictions must be non-local. It has been pointed
> out by both Albert [A] and Cramer [C] (who both support different
> interpretations of QM) that Bell and Eberhard had implicity assumed that
> every possible measurement - even if not performed - would have yielded a
> single definite result. This assumption is called contra-factual
> definiteness or CFD [S].
If it is allowed to throw classical dices (that means dices described
by some classical probability theory) to create the outcomes of the
experiments Bell's inequality remains unchanged. In this sense,
experiments having a "single definite result" does not seems to be the
point.
> What Bell and Eberhard really proved was that every quantum theory
> must either violate locality or CFD. Many-worlds with its
> multiplicity of results in different worlds violates CFD, of course,
> and thus can be local.
Multiplicity of results is something you can have in a classical world
too. Simply throw classical dices to "split worlds". In such a
classical "many worlds" theory Bells' inequality holds. Thus, the
"many worlds" and "splitting" language looks like a smokescreen which
hides the nature of the differences between "many worlds" and a
realistic theory.
And the point is that we have to replace classical probability theory
on the space of the "many worlds" with something else, "quantum
logic", to obtain the QM results. Something which has to be assumed
from the start - but which is OTOH the thing which we want to explain.
Daniel Davis
Hello, Tim.
Tim S <T...@timsilverman.demon.co.uk> wrote in message news:<BA59B451.12030%T...@timsilverman.demon.co.uk>...
> on 25/1/03 7:43 pm, Daniel Davis at buybuyd...@yahoo.com wrote:
> <Jaynes' and hidden-variable interpretations>
>
> > No - the correlations result from the hidden variable L and the
> > specifics of how , when, and where you measure.
>
> This can't be true if Jaynes' argument is to work against Bell's Theorem.
Easy to say. Can you show it?
> >> Again
> >> these seemingly random choices of the experimenter (and the polarizer
> >> manufacturers etc.) are conspiring to give the appearance of
> >> non-locality!
> >
> > I assume that you don't find it strange that experimental measurements
> > depend on
> > the specifics of how you take the measurements.
>
> Yes, but the results of independent experiments shouldn't be correlated.
I invite you to demonstrate clearly what you are claiming about
independence using P( | ) notation. Your comment doesn't have enough
precision for me to be sure I know what you are claiming.
Comments like these makes Jaynes more credible to me. On the face of
it, ti is ircular in the context of the point under contention. You
say the measurements are independent. The whole point of a hidden
variable theory is to say that the measurements are both dependent on
the same hidden variable. Assuming independence assumes away the
possibility of a hidden variable theory.
> >> It's just that the dependencies need to be
> >> conspiratorial, given the freedom of the experimenter. Note that these
> >> dependencies may just as well be probablistic as deterministic -- that
> >> is a completely distinct issue. The issue here is not determinism but
> >> locality.
> >
> > The conspiring language leads me to believe that Jaynes objections
> > that Bell has confused conditional probabilities with causation are
> > possibly on the mark.
>
> I don't think you fully appreciate the depth of the conspiracy that's
> required....
Your examples were all very entertaining, but you haven't shown how
they are relevant. I invite you to show why a conspiracy is required.
> Jaynes is effectively claiming that the real laws of physics _could_ be a
> local hidden-variable theory, if the initial conditions had been maliciously
> set up to make it look like quantum theory.
He makes no such claim. That is your claim. It is up to you to show
that it is in fact what Jaynes is "effectively claiming".
I make the same invitation to you as I did to Eric. I'll handle Jaynes
side of the argument. You handle Bell's. I'm not constitutionally
opposed to ontological randomness - or non-locality, for that matter.
We'll see if Bell's proof stands up.
Michael C Price
>> All the experiments attempting to test EPR/Bell's
>> inequality to date (including Aspect's in the 1980s [As])
>> are in line with the predictions of standard QM
>> - hidden variables are ruled out.
> A "local" forgotten - Bohmian mechanics is not ruled out.
Correct, I should have said
"local hidden variables are ruled out."
See my response to Oz for my comments on FTL.
Daniel Davis
> buybuyd...@yahoo.com (Daniel Davis) writes:
> Which was never Bell's claim. Instead, Bell has started from Bohmian
> mechanics - a quite simple hidden variable theory - which has one
> uncommon and unpopular property: non-locality (a need for a preferred
> frame).
>
> His aim was to prove that this particular feature is no accident but a
> necessity for hidden variable theories.
My understanding of the import of Bell's claims is that "there are no
local hidden variable theories."
> And it leads me to believe that Jaynes objections are off the mark.
Could be. But are you sure that you understand Jaynes well enough to
know? I'm sure that I don't understand Bell well enough to know that
he is off the mark, but objections I've seen to Jaynes have been
consistently off base, and his objections to Bell seem reasonable, if
they are accurate representations of Bell.
If you take the Bell side of the argument, I'll take the Jaynes side,
and we can see which side we like better.
> > Consider a problem. I put a red ball and a white ball in a bag.
> > Without looking, I pull one ball out and put it in an identical bag. I
> > send one bag to NY, and one to LA. A month later, when I open the bag
> > in LA, I know what is in the bag in NY instantaneously.
>
> This gives an example of a correlation which does not violate Bell's
> inequality. Whoever believes this is a valid objection against Bell
The example is meant only as a demonstration of taking non-local
logical dependencies as non-local causal dependencies. In this case,
it is easy to see the error of doing so.
> I recommend you to try to understand the seriousness of violations of
> Bell's inequality from point of view of common sense. I hope
> www.ilja-schmelzer.de/realism/game.html may be helpful.
Your site seemed to be "down for maintenance". I'll try again another
time.
What I want to understand are the actual conditions that Bell's
inequalities relate to. Does the derivation of the inequalities in
fact rule out local hidden variable theories? I know that you (and
others) think the answer is yes, but Jaynes thinks no.
> > Regardless of Bell's inequality gymnastics, if a hidden variable
> > theory could produce that joint distribution, then Bell would be shown
> > to be wrong, correct?
>
> A local one, yes.
Thank you.
> > When Jaynes says, "QM gives", what does he mean? Where does this
> > equation come from?
>
> That's indeed simple standard two-particle QM, but the main advantage
> is that there is no much necessity for laymen to care about the QM
> derivation: Nobody is questioning this part of the derivation,
I wish to see it because I haven't seen it and I thought it could shed
light on the issue for me. I'm not looking to argue with the
derivation.
> moreover there are experimental results in support of the QM
> prediction which show that the point is one about Nature against one
> of the assumptions of local realism.
I'd also like to know what the actual data is that claims to support
P(AB|ab) = 0.5 ( sin(theta/2) )^2. There is data, and there is
interpretation of data. Detector efficiency seems particularly
relevant in this regard.
> BTW, I see exactly no reason to give up realism.
I'm kind of partial to it.
> The violation
> therefore simply proves the existence of faster than light causal
> influences, that's all.
I'm more partial to realism than causal speed limits, but I'm not
convinced that either has to go.
Bennett Standeven
To be precise, I'm going to consider the following setup:
My friend on Mars decides to send either an A or a B over the FTL
phone. Then my friend sends the same letter over an ordinary radio.
> > The initial state of the wavefunction of you, me and the electrons and the
> > rest of the universe may be written:
> >
> > |psi> = |me> |electrons> |you> |rest of universe>
> > on in on
> > Earth deep Alpha
> > space Centauri
> > or more compactly, ignoring the rest of the universe, as:
> > |psi> = |me, electrons, you>
> And
> > |me> represents me on Earth with my detection apparatus.
> > |electrons> = (|+,-> - |-,+>)/sqrt(2)
> > represents a pair electrons, with the first electron travelling
> > towards Earth and the second electron travelling towards Alpha
> > Centauri.
> >
> > |+> represents an electron with spin in the +z direction
> > |-> represents an electron with spin in the -z direction
>
> Not much necessity to change anything. Maybe replacing "electron"
> with "FTL-phone".
>
Here we have |me> representing me with the FTL phone and a receiver,
|you> representing the person on Mars, and |letter> representing the
letter chosen by you.
> > It is an empirically established fact, which we just have to accept, that we
>
> Hm, it seems that we can already stop here. An "explanation"
> containing such a phrase is not an explanation. This seems obvious,
> independent on our FTL phone argumentation. But, of course, we can
> give an FTL phone explanation in a simple way:
>
> "It is an empirically established fact, which we just have to accept,
> that the FTL phone works."
>
For my setup, the "empirically established fact" is that if |letter>
is A, then |letter> is A, and similarly for B. I don't see that this
fact requires an explanation...
[...]
> > After having measured the state of the electron my state is described as one
> > of either:
> >
> > |me[l]> represents me + apparatus + records having measured
> > and recorded the x-axis spin as "left"
>
> |me[A,B]> represents me + phone + records having said "A" and having heard "B"
|me[A]> respents me + apparatus + record having heard the FTL phone
say "A".
|me[B]> ditto for "B".
|me[A, B]> represents me + phone _ records having heard "A" from FTL
phone, and
"B" from radio.
similar for other three cases.
[...]
These formulas, however, are quite simple:
psi_1 = |me, letter, you> = (|me, A, you> - |me, B, you>)/sqrt(2)
psi_2 = (|me[A], A, you> - |me[B], B, you>)/sqrt(2)
[...]
> > And see that there are only two copies of you. We have each been split into
> > two copies, each perceiving a different outcome for our electron's spin, but
> > we have not been split by the measurement of the remote electron's spin.
>
> Each of us has been split into two copies, hearing "A" vs. "not A"
> (similarly "B" vs. "not B") on our local phone. But we have not been
> split by the other guy saying something.
>
Right; the splitting is due to our hearing the FTL phone.
> > After you and I communicate our readings to each other, more than four years
> > later, we get:
> >
> > |psi>_3 =
> > (
> > + |me[r,d],right,down,you[d,r]> (i-1)
> > - |me[r,u],right,up,you[u,r]> (i+1)
> > + |me[l,u],left,up,you[u,l]>(1-i)
> > + |me[l,d],left,down,you[d,l]> (1+i)
> > ) /2*sqrt(2)
> > The decomposition into four worlds is forced and unambiguous after
> > communication with the remote system.
>
> The same for the FTL phone. "Superposition" excludes here the
> contradicting outcomes.
>
Specifically, we get:
psi_3 = {|me[A,A], A, you>
- |me[B,B], B, you>
) / sqrt(2)
> > Until the two observers communicated
> > their results to each other they were each unsplit by each others'
> > measurements, although their own local measurements had split themselves.
> > The splitting is a local process that is causally transmitted from system to
> > system at light or sub-light speeds. (This is a point that Everett stressed
> > about Einstein's remark about the observations of a mouse, in the Copenhagen
> > interpretation, collapsing the wavefunction of the universe. Everett
> > observed that it is the mouse that's split by its observation of the rest of
> > the universe. The rest of the universe is unaffected and unsplit.)
>
> This consideration can be taken as it is.
>
Except of course that there is no splitting due to the radio
transmission this time.
> > To recap. Many-worlds is local and deterministic. Local measurements split
> > local systems (including observers) in a subjectively random fashion;
> > distant systems are only split when the causally transmitted effects of the
> > local interactions reach them. We have not assumed any non-local FTL
> > effects, yet we have reproduced the standard predictions of QM.
>
> The same for our explanation of the FTL phone.
>
Except that the split may occur before the "causally transmitted
effects" (i.e. the radio signal) reaches the observer, unlike in the
EPR case. Thus, in this case the many-worlds explanation does not
"work", while in the EPR case it does.
Michael C Price
> OK. This assumes that the particle cannot communicate
> 'internally' at FTL speeds. What if it can? As far as
> I can see there are no paradoxes with this view,
Agreed. My argument only shows that quantum mechanics
is 1) incomplete, 2) requires FTL or 3) many-worlds.
I do think the FTL solution is rather unlikely;
since we observe no FTL commmunication we would
expect any underlying theory to be FTL-free. But
that doesn't mean FTL's impossible.
As an aside, I think this was the jist if Ilja's post
as well, namely that EPR/Bell doesn't exclude FTL
as a possibility - which I agree with. Yes, FTL
is possible. I just find it implausible, less
implausibe than many-worlds.
> whilst there is a de-facto paradox in 'many worlds'.
You haven't explained what the "de-facto paradox in
'many worlds'" is. I think my conclusion - which in no
way appears to contradict your FTL preference - stands:
>> Thus many-worlds is the only local quantum theory in
>> accord with the standard predictions of QM and, so
>> far, with experiment.
Cheers,
Oz
>Oz writes:
>
>> OK. This assumes that the particle cannot communicate
>> 'internally' at FTL speeds. What if it can? As far as
>> I can see there are no paradoxes with this view,
>
>Agreed. My argument only shows that quantum mechanics
>is 1) incomplete, 2) requires FTL or 3) many-worlds.
>
>I do think the FTL solution is rather unlikely;
>since we observe no FTL commmunication we would
>expect any underlying theory to be FTL-free. But
>that doesn't mean FTL's impossible.
If ftl was part of a 'hidden' variable then I wouldn't expect FTL to be
observable.
>As an aside, I think this was the jist if Ilja's post
>as well, namely that EPR/Bell doesn't exclude FTL
>as a possibility - which I agree with. Yes, FTL
>is possible. I just find it implausible, less
>implausibe than many-worlds.
Please yourself. I can't say I've observed more than one of these 'many
worlds', so they are unobservables, too.
>> whilst there is a de-facto paradox in 'many worlds'.
>
>You haven't explained what the "de-facto paradox in
>'many worlds'" is. I think my conclusion - which in no
>way appears to contradict your FTL preference - stands:
>
>>> Thus many-worlds is the only local quantum theory in
>>> accord with the standard predictions of QM and, so
>>> far, with experiment.
Who said a quantum theory had to be local?
As far as I can tell relativity doesn't bother itself with
unobservables. Personally I find it more plausible to postulate an
internal FTL process for QM, than an infinity of many worlds.
Particularly if both methods predict identically then one could say that
many worlds predicts the observed FTL effects and thus my preference
would be for occham's razor to lop off an infinity of worlds for one
simple ftl effect. It's certainly simpler.
Eric Dennis
> ede...@princeton.edu (Eric Dennis) wrote:
> > In his critical quotation of Bell after equation (15), it does seem
> > Jaynes is objecting to P(B|abL) = P(B|bL) as well. He's not explicit
> > on this point, but I agree the urn example is more relevant to the
> > case of omitting the measurement result from the conditioning
> > statement.
> I don't think so. See Jaynes' next paragraph:
> ####
> Note, however, that merely knowing the direction of the A measurement
> does not change any predictions at B [ed. P(B|abL) = P(B|bL) ]...
> As we would expect from (15), it is necessary to know also the result
> of the A measurement before the correlation effects our predictions.
> [ ed. P(B|abL) = P(B|AbL) = P(B|bL) <> P(B|AabL) ]
> ####
>
> You need to know both (a,A) to know anything more about B; either
> alone tells you nothing more.
Here, Jaynes is referring to what quantum mechanics predicts (and it
is well verified experimentally), not to what local hidden variable
theories predict, which is what Bell's argument is about.
> > that all these measured correlations result from pre-existing
> > correlations between the two polarizers (etc.) you happened to pull
> > off the shelf last week when you were setting up the experiment.
> No - the correlations result from the hidden variable L and the
> specifics of how , when, and where you measure.
L contains all information about common causes of the measurement
results at A and B, i.e. everything in the overlap of the past light
cones of A and B. This includes everything about how the experiment
was set-up, how the polarizers were manufactured, etc.
> > Again
> > these seemingly random choices of the experimenter (and the polarizer
> > manufacturers etc.) are conspiring to give the appearance of
> > non-locality!
> I assume that you don't find it strange that experimental measurements
> depend on the specifics of how you take the measurements.
Of course not, as a general statement. But do you see why the
objection from determinism requires huge conspiracies when you think
about what actually must be going on for the events at A and B to be
correlated as they are -- without any actual influence from b to B and
from a to B? The point of Bell's analysis is specifically to exclude
the normal kinds of common-causes that would otherwise be invoked to
explain the correlations, as in your red/white ball example below.
> > No. If you are allowed to tune the spacetime functions just right, you
> > can indeed get the correlations.
>
> Could you demonstrate?
There's nothing to demonstrate. This is merely the statement that the
observed correlations could result from something other than a to B or
b to A causation -- it is just the admission of a "loophole". But it
is a ridiculous loophole as it stands.
> Ok. It seems to me you have granted my first objection to Bell - the
> claim that Bell has proven that there can't be a hidden variable
> theory that accounts for QM measurements is false.
Everyone agrees that NON-LOCAL hidden variable theories can be
consistent with QM. Bell shows that the only way local hidden variable
theories could do this would be by ridiculous conspiracies.
> The conspiring language leads me to believe that Jaynes objections
> that Bell has confused conditional probabilities with causation are
> possibly on the mark.
>
> Consider a problem. I put a red ball and a white ball in a bag.
> Without looking, I pull one ball out and put it in an identical bag. I
> send one bag to NY, and one to LA. A month later, when I open the bag
> in LA, I know what is in the bag in NY instantaneously.
>
> Has the measurement at LA "conspired" with the measurement in NY? Has
> locality been violated? I don't think so. If one wanted to be
> tediously QM, we could have the ball picking determined in the same
> way as for Schroedingers cat. One could claim an instantaneous
> collapse of the wave functions for the balls. What has collapsed is
> our *ignorance* about which ball is where.
This is exactly correct. But this is also exactly the kind of
common-cause account that Bell's analysis excludes for the delayed
choice experiments. Take a look at "Professor Bertlmann's socks and
the nature of reality" in Bell's compilation *Speakable and
unspeakable in quantum mechanics*. Bell hits this issue squarely.
I don't have the time to reconstruct a full account of Bell
inequalities here. I strongly recommend this compilation though. There
is an essay there called, I think, "The theory of local beables" that
is particularly good.
You might also like something I wrote at
http://www.objectivescience.com/articles/ed1_quantum_dissidents.htm
which addresses some of the things you're bringing up.
Daniel Davis
Ralph Hartley <har...@aic.nrl.navy.mil> wrote:
> Daniel Davis wrote:
> > ...
> > In this vein, I may in fact agree with Jaynes after all. He later
> > states that he thinks Einstein would have liked time varying theories.
> > (Why not dependencies on spacetime intervals?). In such a case, you
> > have to be very careful that you have enough info in "aL", like
> > precise time intervals, to actually determine A - if you don't, then
> > "Bb" may carry additional info for predicting A, and so the
> > simplification P(A|BabL) = P(A|aL) will in fact be incorrect. Seen in
> > this way, I can agree with Jaynes.
> But any information avilable at both measurements is part of L, by
> definition. "Bb" is information local to the second measurement but NOT the
> first. Sure, the exact timing of the second measurement could be correlated
> with the outcome of the first, but unless that were part of L, that would
> violate locality.
Please. Use some notation so we both can be clear on just what you are
claiming. From your comments, I think you are committing just the
errors that Jaynes claimed Bell did: confusing correlation with
causation, and not treating time variation properly. But I don't think
its productive to play mind reader.
Ok. Let me set up Jaynes' notation. I'll add a little too.
A_p,B_p : the two particles
A,B: spin measured up for A_p,B_p
a,b: polarization of detectors
xt: (time, location) for an event
a_xt,b_xt:(time,location) of measurement for A,B on A_p, B_p
L_xt: (time,location) of event where A_p,B_p are created and
are together
L_a,L_b: local hidden variables determined at L_x in creation of
A_p,B_p
Note that I have two L: L_a,L_b. Don't get too worked up over that.
That is just for conservation laws. L_a and L_b should be related, as
in L = L_a = -L_b. Making this distinction clear allows for P(A|...)
to have the same functional form as P(B|....). But, let's just write
things as L, with an understanding of the issues I just brought up in
case symmetry arguments are brought to bear.
To simplify further, the whole xt business is trying to account for
spacetime intervals. I'd be happy for all the spacetime business to be
subsumed in the time intervals between L_xt and a_xt,b_xt: a_t,b_t.
So, the simplified model is:
A_p,B_p: names for the two particles
A,B: spin measured up for A_p,B_p
a,b: polarization of detectors
a_t,b_t: (delta time) of measurement for A,B on A_p, B_p
L: local hidden variable determined at L_xt in creation of
A_p,B_p
Note also that I'm going beyond Jaynes in one very important way - I'm
trying to give what I consider a complete class of reasonable hidden
variable theories. Bell created his class of hidden variable theories
- Jaynes calls them Bell theories - and Jaynes pointed out that Bell
theories didn't encompass all hidden variable theories. However,
Jaynes didn't offer an alternative class of theories. He wasn't
required to, as Bell had the burden of proof, since he was trying to
show that no hidden variable theory could possibly explain the
correlations observed.
Proving that Bell's argument works on this class of theories wouldn't
definitively refute Jaynes, but I think it would deal a blow to some
of his arguments against Bell.
By my notation, I would expect:
P(AB|a,a_t,L, b,b_t,L)
= P(A|B, a,a_t,L, b,b_t,L) P(B|a,a_t,L, b,b_t,L)
= P(A|B, a,a_t,L, b,b_t,L) P(B|b,b_t,L)
= P(A|a,a_t,L) * P(B|b,b_t,L)
Note: I'm not sure if Jaynes would go for the last step. I think he is
fine up til there. Jaynes objects to: P(A|BabL) = P(A|aL). Bell
doesn't explicitly account for time, and Jaynes says that the rest of
Bell's derivation does not hold if we assume time is in L. I think
Jaynes shouldn't object once time is explicitly accounted for. I think
the general issue is: B can be removed from a conditioning statement
for A if A is also conditioned on variables that determine A.
Otherwise, B may contain relevant information for A.
A,B would be independent, *conditioned on the given variables*. A
nice, tidy, set of local theories. If you wish to marginalize out
certain variables in your derivation of inequalities, you bear the
burden of proof as to the validity of that marginalization.
> > As an aside, how could you ever disprove that a supposed "random"
> > event in fact deterministically depended on a hidden variable, but
> > that dependency was subject to oscillation in spacetime much finer
> > than your ability to measure?
> >
> > So, it looks random with current means of measurement, but is
> > determined.
> But the violation of Bell's inequality is a matter of things looking too
> deterministic, not too random.
That may be the problem for a believer in ontological randomness, but
from Jaynes' perspective, he wants a deterministic cause and
epistemological randomness. In this particular case, I have to account
for the randomness in the result. Time oscillation is a natural way
for seeming randomness to enter into a deterministic process.
My comments were meant to show that believers in ontological
randomness can never disprove that a "non-conspiratorial"
deterministic cause does not exist beyond their ability to measure.
> It is possible in principle that the "arbitrary" choices "a" and "b" could
> be determined (from L) in just the right way to give the correlations, but
> since "a" and "b" can be produced by an arbitrary mechanism (which the
> experimenter chooses) this would reqire an increadible conspiracy.
You're the third person to make the *claim* that some conspiracy is
required. You're the third person I'll invite to defend Bell while I
defend Jaynes.
But let's do it in the notation I just set up, ok?
Ilja Schmelzer
buybuyd...@yahoo.com (Daniel Davis) writes:
> Ilja Schmelzer <schm...@wias-berlin.de> wrote in message
>> buybuyd...@yahoo.com (Daniel Davis) writes:
>> Which was never Bell's claim. Instead, Bell has started from Bohmian
>> mechanics - a quite simple hidden variable theory - which has one
>> uncommon and unpopular property: non-locality (a need for a preferred
>> frame).
>> His aim was to prove that this particular feature is no accident but a
>> necessity for hidden variable theories.
> My understanding of the import of Bell's claims is that "there are no
> local hidden variable theories."
And, therefore, there is no need to "improve" (nonlocal) Bohmian
mechanics in this direction.
>> And it leads me to believe that Jaynes objections are off the mark.
> Could be. But are you sure that you understand Jaynes well enough to
> know?
I don't like to make claims of type "I'm sure I understand him well
enough". But Jaynes position - as I have (probably mis)understood it
is a reasonable position for somebody who has not understood the
seriousness of violations of Bell's inequality.
> If you take the Bell side of the argument, I'll take the Jaynes side,
> and we can see which side we like better.
Fine.
>>> Consider a problem. I put a red ball and a white ball in a bag.
>>> Without looking, I pull one ball out and put it in an identical bag. I
>>> send one bag to NY, and one to LA. A month later, when I open the bag
>>> in LA, I know what is in the bag in NY instantaneously.
>> This gives an example of a correlation which does not violate Bell's
>> inequality. Whoever believes this is a valid objection against Bell
> The example is meant only as a demonstration of taking non-local
> logical dependencies as non-local causal dependencies. In this case,
> it is easy to see the error of doing so.
So far, ok.
>> www.ilja-schmelzer.de/realism/game.html may be helpful.
> Your site seemed to be "down for maintenance". I'll try again another
> time.
It seems to be back.
> What I want to understand are the actual conditions that Bell's
> inequalities relate to. Does the derivation of the inequalities in
> fact rule out local hidden variable theories? I know that you (and
> others) think the answer is yes, but Jaynes thinks no.
An IMHO correct description of the situation.
>>> When Jaynes says, "QM gives", what does he mean? Where does this
>>> equation come from?
>>
>> That's indeed simple standard two-particle QM, but the main advantage
>> is that there is no much necessity for laymen to care about the QM
>> derivation: Nobody is questioning this part of the derivation,
>
> I wish to see it because I haven't seen it and I thought it could shed
> light on the issue for me. I'm not looking to argue with the
> derivation.
AFAIR Bell's original article (reprinted in "Speakable and
Unspeakable") is a good place. Anyway this book is highly recommended
reading.
> I'd also like to know what the actual data is that claims to support
> P(AB|ab) = 0.5 ( sin(theta/2) )^2. There is data, and there is
> interpretation of data. Detector efficiency seems particularly
> relevant in this regard.
Of course detector efficiency is a loophole. With inefficient
detectors you cannot win the game described in
www.ilja-schmelzer.de/realism/game.html.
>> The violation therefore simply proves the existence of faster than
>> light causal influences, that's all.
> I'm more partial to realism than causal speed limits, but I'm not
> convinced that either has to go.
Let's see. IMHO to accept a VBI (violations of Bell's inequality)
as a proof of violations of Einstein causality we need two things
which are often questioned but which should not be questioned
from point of view of idealized common sense (Jaynes robot).
The first is the acceptance of independence of free choice of
experimenters. There is, obviously, the logical loophole of
predetermination.
But there is another situation where questioning the free choice of
the experimenter leads to nonsensical results. Einstein causality
tells us that there are no FTL phones. Thus, if we observe in reality
some FTL phone, Einstein causality is false. But there may be some
(unreasonable) argumentations which, even if confronted with a working
FTL phone, could be used to defend Einstein causality. Such
argumentations we would like to exclude from idealized common sense.
Now, pointing out in general terms that correlation is not causation
(this is what I see in Jaynes) as well as questioning the independence
of the free decisions of the experimenters are argumentations of this
type. Last not least, whatever we do testing if something named "FTL
phone" really works is observing correlations between free choices of
experimenters and observations.
The other point is the indirect character of the observation. What we
observe has two possible realistic explanations: A->B or B->A. The
typical case of an indirect observation: every realistic explanation
contains the "indirectly observed" thing, therefore we conclude,
indirectly, that thing really exists. I doubt that a reasonable
person would like to exclude indirect observation from science.
But there is a quite popular argument which relies on the indirect
character of this observation: we cannot use the correlations to
transfer information. Of course, we cannot, if we could transfer it
from A to B this would be in contradiction with the possible
explanation B->A. Again, if confronted with a situation where "A->B
or B->A" we would not like to accept reasoning which makes us believe
"not(A->B or B->A)" via "we cannot use this for information transfer".
Ilja Schmelzer
>>> [a "many worlds explanation" of violations of Bell's inequality]
>> Is this really an explanation? I propose the "FTL phone" test to this
>> "explanation". The basic idea is the following: Assume we have found
>> or created a device which works like an FTL phone. So you can use it
>> to talk with a Mars station without any delay for the speed of light.
>> It is reasonable that in this case Einstein causality should be
>> rejected. And that any "explanation" of this phone which preserves
>> Einstein causality is simply nonsense, and not an explanation. Now,
>> given some "explanation" of EPR experiments, we can try to use a
>> similar "explanation" for the FTL phone. If this replacement works,
>> the "explanation" should be rejected as nonsensical.
> To be precise, I'm going to consider the following setup:
> My friend on Mars decides to send either an A or a B over the FTL
> phone. Then my friend sends the same letter over an ordinary radio.
Fine. But note that in this case I have to fake the "many worlds
explanation" as an explanation, and you have to fix the fault in this
"explanation".
It's not that easy for me, because I really don't believe that "many
worlds" gives an explanation. Therefore, I can really do it only in
one direction: you give a "many worlds" explanation of EPR, and I use
copy and paste to fake an explanation for the FTL phone.
IOW, the question is not if my "many worlds" explanation of an FTL
phone works. It doesn't, I know it myself. My argument is that the
original explanation does not work too. The question is why many
worlds of EPR is an explanation but my many worlds parody of FTL
explanation isn't.
>>> It is an empirically established fact, which we just have to
>>> accept, that we
>> Hm, it seems that we can already stop here. An "explanation"
>> containing such a phrase is not an explanation. This seems obvious,
>> independent on our FTL phone argumentation. But, of course, we can
>> give an FTL phone explanation in a simple way:
>> "It is an empirically established fact, which we just have to accept,
>> that the FTL phone works."
> For my setup, the "empirically established fact" is that if |letter>
> is A, then |letter> is A, and similarly for B. I don't see that this
> fact requires an explanation...
Here you propose something different from my fake of the original
"explanation". Below you conclude that _your_ fake doesn't work. So
you have proven that you are able to construct an explanation of an
FTL phone which does not work. That's fine but irrelevant.
You should have to show not that my parody "It is an empirically
established fact, which we just have to accept, that the FTL phone
works." is not an explanation (which is quite obvious, and the
intention of my parody) but that the original consideration containing
"It is an empirically established fact, which we just have to accept,
that ..." has some nontrivial explanatory value.
>> Of course, we can also support the FTL-phone explanation with
>> formulas.
> These formulas, however, are quite simple:
> psi_1 = |me, letter, you> = (|me, A, you> - |me, B, you> )/sqrt(2)
> psi_2 = (|me[A], A, you> - |me[B], B, you> )/sqrt(2)
How can you decide "these formulas are"?
The "FTL phone explanation" is something existing in my head as a
parody of a "many worlds explanation". It is about a hypothetical
world which is different from our own, a world where an FTL phone
really exists. Therefore, scientists in this world may have a theory
which describes their observations correctly, but in this case this
theory is not our relativistic QFT. Moreover, the story about this
hypothetical worlds has been written down only partially. I was to
lazy to write down formulas, in this sense they simply don't exist.
What exists is only a general proposal how to create such a fake:
<unsnip>
>> Especially we take them from some causal realistic FTL-violating
>> theory - the analogon of Bohmian mechanics. This theory depends, as
>> Bohmian mechanics, from a preferred time T.
</unsnip>
Of course, if you would like to support my parody you could have
supported my parody with a specific proposal for fake formulas. But
this would be meaningless if it does not work (which is your
conclusion below). As a counterargumentation you would have to show
that it is impossible to support the fake with a set of consistent
formulas following the proposal I have made - or that the original
explanation has other interesting properties which give it explanatory
power, properties which cannot be faked in the case of an FTL phone.
>>> Until the two observers communicated their results to each other
>>> they were each unsplit by each others' measurements, although
>>> their own local measurements had split themselves. The splitting
>>> is a local process that is causally transmitted from system to
>>> system at light or sub-light speeds. (This is a point that Everett
>>> stressed about Einstein's remark about the observations of a
>>> mouse, in the Copenhagen interpretation, collapsing the
>>> wavefunction of the universe. Everett observed that it is the
>>> mouse that's split by its observation of the rest of the
>>> universe. The rest of the universe is unaffected and unsplit.)
>> This consideration can be taken as it is.
> Except of course that there is no splitting due to the radio
> transmission this time.
The splitting is a trivial one, the probability of |me[A,B]> is zero.
This makes the FTL explanation even simpler. And in itself it is
simply an empirically established fact which does not need further
explanation. [This is the main point of the fake. It is the
particular value of the probability P(|me[A,B]>)=0 which really
requires explanation. MWI does not give any such explanation for QM
probabilities and therefore does not "explain" anything interesting.]
>>> To recap. Many-worlds is local and deterministic. Local measurements split
>>> local systems (including observers) in a subjectively random fashion;
>>> distant systems are only split when the causally transmitted effects of the
>>> local interactions reach them. We have not assumed any non-local FTL
>>> effects, yet we have reproduced the standard predictions of QM.
>> The same for our explanation of the FTL phone.
> Except that the split may occur before the "causally transmitted
> effects" (i.e. the radio signal) reaches the observer, unlike in the
> EPR case.
There is no difference. A split for A occurs at the time of
observation by A of something - be it the FTL signal or the radio
signal. As well we have two splits in the EPR case - A observing his
result of measurement and A receiving the radio signal about the other
result.
By the "empirically established fact" the second split in the FTL case
is one with trivial probability distribution 1:0. This is something
which we (according to the "FTL explanation") simply have to accept.
What is left unexplained here but explained in MWI?
> Thus, in this case the many-worlds explanation does not "work",
> while in the EPR case it does.
It works as well, that means, it doesn't work in above cases.
Oz
>Which was never Bell's claim. Instead, Bell has started from Bohmian
>mechanics - a quite simple hidden variable theory - which has one
>uncommon and unpopular property: non-locality (a need for a preferred
>frame).
>
>His aim was to prove that this particular feature is no accident but a
>necessity for hidden variable theories. This essentially weakens the
>objection "needs a preferred frame" against Bohmian mechanics.
I have a small question that I have recently formulated a reasonable
analogy. Perhaps you could answer it.
Let's take some device that spits out two entangled particles. They are
entangled (say) by spin. Now imagine the spin in the following way:
the two particles have a spin direction represented as an arrow on a
paper disc and the two particles are attached by a rigid shaft so at all
times the arrows points in opposing directions. That is, the spins are
correlated.
Am I right (and I suspect strongly that I am not) in assuming that this
setup would give essentially the same statistics as a real entangled
particle-pair?
John Baez
Oz <ozac...@despammed.com> wrote:
>I have a small question that I have recently formulated a reasonable
>analogy. Perhaps you could answer it.
>
>Let's take some device that spits out two entangled particles. They are
>entangled (say) by spin. Now imagine the spin in the following way:
>
>the two particles have a spin direction represented as an arrow on a
>paper disc and the two particles are attached by a rigid shaft so at all
>times the arrows points in opposing directions. That is, the spins are
>correlated.
>
>Am I right (and I suspect strongly that I am not) in assuming that this
>setup would give essentially the same statistics as a real entangled
>particle-pair?
You're right: you're wrong. The whole point of Bell's theorem
is that it says you can't envision particles with entangled spins
as two little classical arrows that are constrained to point in
opposite directions. The theorem basically says that such a model
can't possibly match the statistics that quantum mechanics predicts -
and which we actually observe.
Indeed, if you could model quantum entanglement as you suggest,
people wouldn't regard it as "spooky" and rant about it until
their faces turn purple and they keel over frothing at the mouth.
Daniel Davis
>
> > You need to know both (a,A) to know anything more about B; either
> > alone tells you nothing more.
>
> Here, Jaynes is referring to what quantum mechanics predicts (and it
> is well verified experimentally), not to what local hidden variable
> theories predict, which is what Bell's argument is about.
He seems to be referring to both QM and the "fundamentally correct"
probability relations, showing that QM and those relations in (15)
both predict that one must know both (a,A) to know anything more about
B.
I refer again to:
####
As we would expect from (15) [ed. the fundamentally correct
probability relations, P(AB|abL) = P(A|abL)P(B|AabL)], it is necessary
to know also the result of the A measurement before the correlation
effects our predictions.
####
Jaynes is making the point that the QM relations are in agreement with
the correct relations for a local hidden variable theory as far as
Jaynes would derive them, but they are not in agreement with the
relations Bell would ascribe to arbitrary local hidden variable
theories.
And back to the original points, Jaynes does not object to
P(A|abL) = P(A|aL),
he objects to (14), Bell's
(14) P(AB|abL) = P(A|aL)P(B|bL)
which contradicts the "fundamentally correct" relations
(15) P(AB|abL) = P(A|abL)P(B|AabL)
He doesn't seem to think that Bell has justified his jump to (14) from
(15), quotes Bell justification, where Bell equates causal
independence with logical independence, notes that that is an
erroneous assumption by Bell, and so feels free to reject the notion
that (14) is the proper way to characterize all local hidden variable
theories.
He goes on to point out that Bell's derivation fails to take into
account time varying local hidden variable theories as well.
> But do you see why the
> objection from determinism requires huge conspiracies when you think
> about what actually must be going on for the events at A and B to be
> correlated as they are -- without any actual influence
> from b to B [ed. a to B?] and
> from a to B?
No, I don't. The requirement for a conspiracy is an interpretation,
not some fact of nature carved in granite. I don't say that I can't be
persuaded, but I haven't seen anything that has persuaded me.
> The point of Bell's analysis is specifically to exclude
> the normal kinds of common-causes that would otherwise be invoked to
> explain the correlations, as in your red/white ball example below.
That is what Bell attempts to do. Jaynes would say that he fails. The
failure to take time variation into account is a clear example of that
failure.
>From Jaynes, I see two basic objections:
1) Bell's argument for jumping from (15) to (14), *as given and
quoted*, is incorrect, confusing causal and logical independence.
2) Even if a valid argument for (15) to (14) can be found, the lack of
time dependence in the equations would guarantee that time varying
local hidden variable theories had not been addressed.
Both objections look sound to me. Bell's argument, as quoted, is
mistaken. And it is not immediately apparent that Bell's derivation
would survive time varying local hidden variable theories.
> Take a look at "Professor Bertlmann's socks and
> the nature of reality" in Bell's compilation *Speakable and
> unspeakable in quantum mechanics*. Bell hits this issue squarely.
Seems to be of print. Any other recommendation?
> You might also like something I wrote at
>
> http://www.objectivescience.com/articles/ed1_quantum_dissidents.htm
That site, www.objectivescience.com, repeatedly bumped me over to:
http://www.bahamas2000.com/forsale/
Ilja Schmelzer
> I have a small question that I have recently formulated a reasonable
> analogy. Perhaps you could answer it.
>
> Let's take some device that spits out two entangled particles. They are
> entangled (say) by spin. Now imagine the spin in the following way:
>
> the two particles have a spin direction represented as an arrow on a
> paper disc and the two particles are attached by a rigid shaft so at all
> times the arrows points in opposing directions. That is, the spins are
> correlated.
>
> Am I right (and I suspect strongly that I am not) in assuming that this
> setup would give essentially the same statistics as a real entangled
> particle-pair?
Your suspection is correct, you are not right. Your setup is a
classical local hidden variable theory where Bell's inequality holds.
I recommend you www.ilja-schmelzer.de/realism/game.html
Oz
Oz:
>>Am I right (and I suspect strongly that I am not) in assuming that this
>>setup would give essentially the same statistics as a real entangled
>>particle-pair?
>
>You're right: you're wrong.
Rather thought so.
>The whole point of Bell's theorem
>is that it says you can't envision particles with entangled spins
>as two little classical arrows that are constrained to point in
>opposite directions. The theorem basically says that such a model
>can't possibly match the statistics that quantum mechanics predicts -
>and which we actually observe.
OK, that's fine.
It would be really nice to have an example showing this difference.
Just to make it clear what the difference is.
>Indeed, if you could model quantum entanglement as you suggest,
>people wouldn't regard it as "spooky" and rant about it until
>their faces turn purple and they keel over frothing at the mouth.
Indeed so, I had noticed.
This from supposedly rational level-headed physicists, too.
michaelprice
> MWI does not give any such explanation for QM
> probabilities and therefore does not "explain" anything
> interesting.
No, many-worlds does explain probabilities:
>From the many-worlds FAQ:
Q23 How do probabilities emerge within many-worlds?
Everett demonstrated [1], [2] that observations in each world obey all the
usual conventional statistical laws predicted by the probabilistic Born
interpretation, by showing that the Hilbert space's inner product or norm
has a special property which allows us to makes statements about the worlds
where quantum statistics break down. The norm of the vector of the set of
worlds where experiments contradict the Born interpretation ("non-random" or
"maverick" worlds) vanishes in the limit as the number of probabilistic
trials goes to infinity, as is required by the frequentist definition of
probability. Hilbert space vectors with zero norm don't exist (see below),
thus we, as observers, only observe the familiar, probabilistic predictions
of quantum theory. Everett-worlds where probability breaks down are never
realised.
Strictly speaking Everett did not prove that the usual statistical laws of
the Born interpretation would hold true for all observers in all worlds. He
merely showed that no other statistical laws could hold true and asserted
the vanishing of the Hilbert space "volume" or norm of the set of "maverick"
worlds. DeWitt later published a longer derivation of Everett's assertion
[4a], [4b], closely based on an earlier, independent demonstration by Hartle
[H]. What Everett asserted, and DeWitt/Hartle derived, is that the
collective norm of all the maverick worlds, as the number of trials goes to
infinity, vanishes. Since the only vector in a Hilbert space with vanishing
norm is the null vector (a defining axiom of Hilbert spaces) this is
equivalent to saying that non-randomness is never realised. All the worlds
obey the usual Born predictions of quantum theory. That's why we never
observe the consistent violation of the usual quantum statistics, with, say,
heat flowing from a colder to a hotter macroscopic object. Zero-probability
events never happen.
Of course we have to assume that the wavefunction is a Hilbert space vector
in the first place but, since this assumption is also made in the standard
formulation, this is not a weakness of many-worlds since we are not trying
to justify all the axioms of the conventional formulation of QM, merely
those that relate to probabilities and collapse of the wavefunction.
In more detail the steps are:
1) Construct the tensor product of N identical systems in state |psi>,
according to the usual rules for Hilbert space composition (repeated indices
summed):
|PSI_N> = |psi_1>*|psi_2>*...... |psi_N> where
|psi_j> = jth system prepared in state |psi>
= |i_j><i_j|psi> (ie the amplitude of the ith eigenstate
is independent of which system it is in)
so that
|PSI_N> = |i_1>|i_2>...|i_N><i_1|psi><i_2|psi>...<i_N|psi>
2) Quantify the deviation from the "expected" Born-mean for each
component of |PSI_N> with respect to the above |i_1>|i_2>...|i_N>
basis by counting the number of occurrences of the ith
eigenstate/N. Call this number RF(i). Define the Born-deviation
as D = sum(i)( (RF(i) - |<i|psi>|^2)^2 ). Thus D, loosely
speaking, for each N length sequence, quantifies by how much the
particular sequence differs from the Born-expectation.
3) Sort out terms in the expansion of |PSI_N> according to whether D
is less/equal to (.LE.) or greater than (.GT.) E, where E is a
real, positive constant. Collecting terms together we get:
|PSI_N> = |N,"D.GT.E"> + |N,"D.LE.E">
worlds worlds
for whichfor which
D > E D <= E
4) What DeWitt showed was that:
<N,"D.GT.E"|N,"D.GT.E"> < 1/(NE) (proof in appendix of [4b])
Thus as N goes to infinity the right-hand side vanishes for all
positive values of E. (This mirrors the classical "frequentist"
position on probability which states that if event i occurs with
probability p(i) then the proportion of N trials with outcome i
approaches p(i)/N as N goes to infinity [H]. This has the
immediate benefit that sum(i) p(i) = 1.) The norm of |N,"D.LE.E">,
by contrast, approaches 1 as N goes to infinity.
Note: this property of D is not shared by other definitions, which
is why we haven't investigated them. If, say, we had defined, in
step 2), A = sum(i)( (RF(i) - |<i|psi>|)^2 ), so that A measures
the deviation from |psi|, rather than |psi|^2, then we find that
does not have the desired property of vanishing as N goes to
infinity.
5) The norm of the collection of non-random worlds vanishes and
therefore must be identified with some complex multiple of the null
vector.
6) Since (by assumption) the state vector faithfully models reality
then the null vector cannot represent any element of reality, since
it can be added to (or subtracted from) any other state vector
without altering the other state vector.
7) Ergo the non-random worlds are not realised, without making any
additional physical assumptions, such the imposition of a measure.
Note: no finite sequence of outcomes is excluded from happening,
since the concept of probability and randomness only becomes
precise only as N goes to infinity [H]. Thus, heat could be
observed to flow from a cold to hotter object, but we might have
to wait a very long time before observing it. What is excluded
is the possibility of this process going on forever.
The emergence of Born-style probabilities as a consequence of the
mathematical formalism of the theory, without any extra interpretative
assumptions, is another reason why the Everett metatheory should not be
regarded as just an interpretation. (See "Is many-worlds (just) an
interpretation?") The interpretative elements are forced by the mathematical
structure of the axioms of Hilbert space.
[H] JB Hartle Quantum Mechanics of Individual Systems American Journal of
Physics Vol 36 #8 704-712 (1968) Hartle has investigated the N goes to
infinity limit in more detail and more generally. He shows that the relative
frequency operator, RF, obeys RF(i) |psi_1>|psi_2>.... = |<i|psi>|^2
|psi_1>|psi_2>...., for a normed state. Hartle regarded his derivation as
essentially the same as Everett's, despite being derived independently.
Eric Dennis
> You're right: you're wrong. The whole point of Bell's theorem
> is that it says you can't envision particles with entangled spins
> as two little classical arrows that are constrained to point in
> opposite directions. The theorem basically says that such a model
> can't possibly match the statistics that quantum mechanics predicts -
> and which we actually observe.
>
> Indeed, if you could model quantum entanglement as you suggest,
> people wouldn't regard it as "spooky" and rant about it until
> their faces turn purple and they keel over frothing at the mouth.
I think this misconstrues the main point of Bell's theorem. Indeed the
theorem is not fundamentally about spin -- or even quantum mechanics
-- at all. Bell says only that certain types of observable
correlations cannot be accounted for by any (relativistically) local
explanation.
What's wrong with Oz's little model is not the impossibility of
regarding spin in some such way, but his failure to include the
effects of the measuring device configurations on the spins and on the
measurement results -- in particular, the effects from the A-side
device on the B-side spin, or vice versa.
Ilja Schmelzer
> "Ilja Schmelzer" <schm...@wias-berlin.de> wrote in message
> news:i3g3cn4...@wias-berlin.de...
>
>> MWI does not give any such explanation for QM
>> probabilities and therefore does not "explain" anything
>> interesting.
>
> No, many-worlds does explain probabilities:
>
>> From the many-worlds FAQ:
Rereading it, I have found the following:
> Q16
> Third, there is no scientific, reductionistic alternative to many-
> worlds. All the other theories fail for logical reasons. (See "Is
> there any alternative theory?")
Sorry, I can accept that somebody does not like Bohmian mechanics, for
various reasons. But that it _fails_ for _logical_ reasons? IMHO this
is simply not serious.
> Q23 How do probabilities emerge within many-worlds?
> Everett demonstrated [1], [2] that
> DeWitt later published a longer derivation of Everett's assertion
> [4a], [4b], closely based on an earlier, independent demonstration by Hartle
> [H].
> Of course we have to assume that the wavefunction is a Hilbert space vector
> in the first place but, since this assumption is also made in the standard
> formulation, this is not a weakness of many-worlds since we are not trying
> to justify all the axioms of the conventional formulation of QM, merely
> those that relate to probabilities and collapse of the wavefunction.
Assuming that the wave function is a Hilbert space vector is fine.
But it is not yet physics. I would guess that we need a little bit
more, some physical assumption. What else is assumed?
> In more detail the steps are:
> 1) Construct the tensor product of N identical systems in state |psi> ,
> according to the usual rules for Hilbert space composition (repeated indices
> summed):
>
> |PSI_N> = |psi_1> *|psi_2> *...... |psi_N> where
> |psi_j> = jth system prepared in state |psi>
> = |i_j> <i_j|psi> (ie the amplitude of the ith eigenstate
> is independent of which system it is in)
> so that
> |PSI_N> = |i_1> |i_2> ...|i_N> <i_1|psi> <i_2|psi> ...<i_N|psi>
>
> 2) Quantify the deviation from the "expected" Born-mean for each
> component of |PSI_N> with respect to the above |i_1> |i_2> ...|i_N>
> basis by counting the number of occurrences of the ith
> eigenstate/N. Call this number RF(i).
"Counting"? A word which sounds like something independent of quantum
theory assumptions. But I don't believe. I guess this "counting"
should be somehow connected with the complex numbers <i_j|psi> .
The following considerations are quite similar to things which have to
be done in BM too, to obtain frequency predictions from the
deterministic evolution of the state of our world. But in BM we have
a clear picture, clear assumptions: The configuration variable
(something we could call "our world" in a many-world-like language)
and a well-defined rule how it changes in time.
> The emergence of Born-style probabilities as a consequence of the
> mathematical formalism of the theory,
Sorry, this cannot be a consequence of mathematical formalism. Math
in, math out. Physics in, physics out. Physics do not appear out of
pure math.
Note: I do not question that the mathematical theorems you have
described are good math, nor that they are important and interesting
results. My question is about the assumptions which have been used.
> Q3 What are the alternatives to many-worlds?
> 2) Hidden Variables [B]. Explicitly non-local. Bohm accepts that all
> the branches of the universal wavefunction exist. Like Everett Bohm
> held that the wavefunction is real complex-valued field which never
> collapses.
So far, fine. All possible worlds is the configuration space, Psi(Q,t)
the complex-valued wave function on this space.
> In addition Bohm postulated that there were particles
> that move under the influence of a non-local "quantum- potential"
> derived from the wavefunction (in addition to the classical
> potentials which are already incorporated into the structure of the
> wavefunction).
A quite artificial description. "Quantum potential" is out of date. I
would describe it in another way. Today we are in the "world"
described by Q_0. What will be our future? This is described by the
guiding equation
d_t Q(t) = <Psi J Psi>/<Psi Psi>
> The implicit, unstated assumption made by Bohm is that only the
> single branch of wavefunction associated with particles can contain
> self-aware observers, whereas Everett makes no such assumption.
I don't understand this. The observer obviously consists of particles.
He is part of some world. And the state of this world is what is
named here "particles".
Now, I simply don't understand what many worlds tells about the
observers. I'm an observer, existing in world Q_0 = Q(t_0). There is
some strange wave function Psi(Q) on the space of all possible worlds
Q. What is their connection? How does this strange function
influence me and what is around me? Assuming many worlds is a
physical theory, I should be able to make some predictions about
future, about Q(t) for t>t_0. What are these predictions?
> Most of Bohm's adherents do not seem to understand (or even be aware
> of) Everett's criticism, section VI [1], that the hidden-variable
> particles are not observable
"Not observable" is standard criticism. But adherents of BM are
realists, they want a clear ontology. Many worlds or not so many, it
should be clear and well-defined what exists. Then, from this
ontology (the theory about what is) we can derive what is observable.
It obviously does not follow that everything should be observable.
> since the wavefunction alone is sufficient to account for all
> observations
Sorry but I don't understand how the wave function is connected with
observation in many worlds at all, so I cannot evaluate this claim. I
read only uncertain verbal descriptions about measurements, splitting
worlds etc.
> The hidden variable particles can be discarded, along with
> the guiding quantum-potential, yielding a theory isomorphic to
> many-worlds, without affecting any experimental results.
I don't see how claims about experimental results follow at all. That
there is some wave function Psi(Q,t) does not seem to define
any measurement or result of measurement.
Ed Keane III
Oz <aco...@btopenworld.com> wrote in message
news:ZIxJ6bDO...@btopenworld.com...
> I have a small question that I have recently formulated a reasonable
> analogy. Perhaps you could answer it.
>
> Let's take some device that spits out two entangled particles. They are
> entangled (say) by spin. Now imagine the spin in the following way:
>
> the two particles have a spin direction represented as an arrow on a
> paper disc and the two particles are attached by a rigid shaft so at all
> times the arrows points in opposing directions. That is, the spins are
> correlated.
>
> Am I right (and I suspect strongly that I am not) in assuming that this
> setup would give essentially the same statistics as a real entangled
> particle-pair?
This is the same as saying that the spin direction must be opposite
and is established at the moment of emission and does give the
same statistical results as an entangled pair. The spooky problem
is that spin can be rotated by the measuring device.
-Ed Keane III
Ilja Schmelzer
Oz <aco...@btopenworld.com> writes:
> >The whole point of Bell's theorem
> >is that it says you can't envision particles with entangled spins
> >as two little classical arrows that are constrained to point in
> >opposite directions. The theorem basically says that such a model
> >can't possibly match the statistics that quantum mechanics predicts -
> >and which we actually observe.
> OK, that's fine.
> It would be really nice to have an example showing this difference.
> Just to make it clear what the difference is.
There are three (red or black) cards on the table so that the color is
not visible to you. Obviously at least one of the following three
statements should be false:
The left and the middle card have the same color.
The right and the middle card have the same color.
The left and the right card have different color.
Now, you have to guess which, and test this by opening two of these
three cards. Obviously, the probability that you find a violation is
at least 1/3.
Now an only slightly more complex variant. Consider two rooms without
any possibility for communication. In every room is a member of my
team and your team. My team claims that we have fixed the colors of
three cards. You and your friend have the right to ask one of the
following three questions:
"What is the color of the left card?"
"What is the color of the middle card?"
"What is the color of the right card?"
You can choose the same or a different question for above rooms. My
team gives an answer "red" or "black" in each room. Now, if your
friend asks the same question as you, our answer should always be the
same. Else, the same rules as before.
Obviously, the probability that you find a violation in these
remaining cases is at least 1/3.
Except, of course, my team has a hidden communication channel.
And, except, of course, that my team has a Bell device without a
detector efficiency loophole.
michaelprice
>> As an aside, I think this was the jist if Ilja's post
>> as well, namely that EPR/Bell doesn't exclude FTL
>> as a possibility - which I agree with. Yes, FTL
>> is possible. I just find it implausible, less
>> implausibe than many-worlds.
> Please yourself. I can't say I've observed more than one of these
> 'many worlds', so they are unobservables, too.
Please yourself, but I observe that one-world theories are riddled
with inconsistencies, whereas the many-worlds theory escapes
from these problems.
>>>> Thus many-worlds is the only local quantum theory in
>>>> accord with the standard predictions of QM and, so
>>>> far, with experiment.
> Who said a quantum theory had to be local?
Well lots of people, actually.... Einstein, Schrodinger...
> As far as I can tell relativity doesn't bother itself with
> unobservables. Personally I find it more plausible to postulate an
> internal FTL process for QM, than an infinity of many worlds.
> Particularly if both methods predict identically then one could say that
> many worlds predicts the observed FTL effects and thus my preference
> would be for occham's razor to lop off an infinity of worlds for one
> simple ftl effect. It's certainly simpler.
Trouble is no one has constructed such a relativistic, non-local quantum
theory to compare many-worlds (which is relativistic and local) with.
Occam's Razor can work when we have 2 or more hypotheses. Since
there is only many-worlds theory that works talk of Occam is premature.
John Baez
Oz <ozac...@despammed.com> wrote:
>John Baez wrote:
>>The whole point of Bell's theorem
>>is that it says you can't envision particles with entangled spins
>>as two little classical arrows that are constrained to point in
>>opposite directions. The theorem basically says that such a model
>>can't possibly match the statistics that quantum mechanics predicts -
>>and which we actually observe.
>OK, that's fine.
>It would be really nice to have an example showing this difference.
>Just to make it clear what the difference is.
It's definitely good to see an example like this.
The first person to come up with one was Bell, and this
is precisely why he's so famous - it's quite ingenious.
Later various people came up with simplified examples.
Unfortunately they all take a little bit of work to explain.
Fortunately, I don't have to do this work, since Gary Felder
already did:
http://www2.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/bell.html
This one is based on an example by Mermin.
You only need a tiny bit of math to follow this example:
for example, you need to know that the cosine of 60 degrees
is 1/2, and you need to know how to add and multiply fractions.
However, you *do* need a fair amount of patience!
>>Indeed, if you could model quantum entanglement as you suggest,
>>people wouldn't regard it as "spooky" and rant about it until
>>their faces turn purple and they keel over frothing at the mouth.
>Indeed so, I had noticed.
>This from supposedly rational level-headed physicists, too.
Right. When supposedly rational people become scared that their
rationality has some mistaken assumptions built into it, they can
get pretty irrational. :-)
PS - By the way, your Christmas card finally reached me here in
Sydney, by a fairly circuitous route. Merry Christmas -
and glad you're all doing well! (Except for the cats....)
You might tell the dissolute Oz Jr. that my friend the Ukrainian
quantum gravity whiz Kirill Krasnov has gotten a position at
Nottingham, where he'll be working with my friend John Barrett.
Oz
>Oz <aco...@btopenworld.com> writes:
>> John Baez wrote:
>> >The whole point of Bell's theorem
>> >is that it says you can't envision particles with entangled spins
>> >as two little classical arrows that are constrained to point in
>> >opposite directions. The theorem basically says that such a model
>> >can't possibly match the statistics that quantum mechanics predicts -
>> >and which we actually observe.
>> OK, that's fine.
>> It would be really nice to have an example showing this difference.
>> Just to make it clear what the difference is.
Thank you for your examples.
I was of course meaning examples using my 'connected twirly Particles'.
Bearing in mind that they are quantum mechanical particles so can
happily be considered as superpositions of two (or more) other
'connected' particle pairs.
Oz
>>Oz:
>> the two particles have a spin direction represented as an arrow on a
>> paper disc and the two particles are attached by a rigid shaft so at all
>> times the arrows points in opposing directions. That is, the spins are
>> correlated.
>>
>> Am I right (and I suspect strongly that I am not) in assuming that this
>> setup would give essentially the same statistics as a real entangled
>> particle-pair?
>
>This is the same as saying that the spin direction must be opposite
>and is established at the moment of emission and does give the
>same statistical results as an entangled pair.
Others disagree.
>The spooky problem
>is that spin can be rotated by the measuring device.
Big deal. I can do that with a few polarising sheets.
The thing is, does rotating the spin, even apparently at an arbitrary
'speed' actually violate relativity? Is the spin actually 'rotated' or
are you just selecting a wavefunction that suits the experimental
results?
michaelprice
thank your for your critique of the many-worlds FAQ. I'll address the
issues you raise in separate posts. Let's examine Bohm here. I shall talk
in terms of non-relativistic models, since these are well handled by Bohmian
mechanics, but bear in mind that many-worlds is trivial to extend
relativistically into a QFT.
>>> From the many-worlds FAQ:
>
> Rereading it, I have found the following:
>
>> Q16
>> Third, there is no scientific, reductionistic alternative to many-
>> worlds. All the other theories fail for logical reasons. (See "Is
>> there any alternative theory?")
>
> Sorry, I can accept that somebody does not like Bohmian mechanics,
> for various reasons.
Actually I *like* Bohmian mechanics. Bohm's 1952 exposition is a
masterpiece of elegance and clarity. The non-relativistic theory is
beautiful and astounding. I am also in complete agreement with its
motivation, namely to have an objectively real model of reality, with
observations emerging only as an epiphenomenon. But I think it fails for
epistemological reasons. More on this later.
> But that it _fails_ for _logical_ reasons? IMHO this
> is simply not serious.
Isn't "epistemological" is a subcategory of "logical"? As I said, more on
this below.
[.....]
>> The implicit, unstated assumption made by Bohm is that only the
>> single branch of wavefunction associated with particles can contain
>> self-aware observers, whereas Everett makes no such assumption.
>
> I don't understand this. The observer obviously consists of
> particles.
I don't see where this "obvious" assumption comes from. In the context of
BM surely the observer, like any other part of reality, consists of
wavefunctions and particles. An observer, like any other part of reality,
could, besides Bohm particles, consist of fields, waves, Hilbert-space
vectors or anything else capable of conveying information. Everett's
contention is that the wavefunction or state vector is the totality of
reality.
But I don't want to get hung up over the definition of an observer; such a
definition is not necessary in either BM or many-worlds. Let's tackle the
ontology before the epistemology.
> He is part of some world. And the state of this world is what is
> named here "particles".
>
> Now, I simply don't understand what many worlds tells about the
> observers.
Many-worlds says the same thing about observers and observations that
Bohmian mechanics does: As you said "Then, from this ontology (the theory
about what is) we can derive what is observable. [i.e. its epistemology]".
So rather than talk directly about observers let's just talk about reality.
In BM there are two classes of real things: There are wavefunctions and
there are particles. All Everett does is to dump Bohm's particles as
Ockhamite excess metaphysical baggage, leaving us with just the
wavefunction.
Why does Everett dump the particles and not the wavefunction? Because there
is a fundamental dichotomy between Bohm-particles and wavefunctions. In BM
the wavefunction evolves according to the conventional wave equations,
whereas the particles' motion is determined entirely by the wavefunction.
The wavefunction acts on the particles, but the particles don't act back on
the wavefunction. This is a big hint that the Bohm-particles are mythical.
Remove the particles and the wavefunction is unaffected.
>> Most of Bohm's adherents do not seem to understand (or even be aware
>> of) Everett's criticism, section VI [1], that the hidden-variable
>> particles are not observable
>
> "Not observable" is standard criticism. But adherents of BM are
> realists, they want a clear ontology. Many worlds or not so many,
> it should be clear and well-defined what exists.
The wavefunction exists at all times and nothing else.
> Then, from this ontology (the theory about what is) we can
> derive what is observable. It obviously does not follow that
> everything should be observable.
Absolutely. For instance the absolute phase and magnitude of the
wavefunction is unobservable. The value of any gauge field is unknown.
>> since the wavefunction alone is sufficient to account for all
>> observations
>
> Sorry but I don't understand how the wave function is connected with
> observation in many worlds at all, so I cannot evaluate this claim.
Observations derive from the wavefunction in Everett's many-worlds in the
same way as observations derive from wavefunction and, putatively, the
hidden-variable Bohm-particles in BM.
> I read only uncertain verbal descriptions about measurements,
> splitting worlds etc.
There is nothing uncertain about the verbal descriptions, once we are clear
about the ontology and epistemology. I deliberately avoided the over-use of
equations in the FAQ because it is concepts I'm trying to get over to the
audience, not technical information.
My conclusion on Bohm still stands:
>> The hidden variable particles can be discarded, along with
>> the guiding quantum-potential, yielding a theory isomorphic to
>> many-worlds, without affecting any experimental results.
Cheers,
Oz
>You only need a tiny bit of math to follow this example:
>for example, you need to know that the cosine of 60 degrees
>is 1/2, and you need to know how to add and multiply fractions.
I ought to be able to follow that, then. However I was hoping for an
example, or at least illustration, using my particles coupled by a rigid
rod. It ought to be an easy and concrete example to show what happens
that shouldn't have. I suspect sticking some polarisers at various
angles on one side is the sort of thing you will want to do.
>>>Indeed, if you could model quantum entanglement as you suggest,
>>>people wouldn't regard it as "spooky" and rant about it until
>>>their faces turn purple and they keel over frothing at the mouth.
>
>>Indeed so, I had noticed.
>>This from supposedly rational level-headed physicists, too.
>
>Right. When supposedly rational people become scared that their
>rationality has some mistaken assumptions built into it, they can
>get pretty irrational. :-)
Heck, been there, got the T-shirt, that's really the point in studying
(however superficially) this sort of stuff. Can you bend your brain to
match reality? OK, it might be easier to deny reality (many do) but it's
more fun not to. For me, the idea that 'total energy' is pretty well
undefined in GR was a stroke to the heart of my quasi-newtonian being
that was quite fun to reorganise my world-view around.
>PS - By the way, your Christmas card finally reached me here in
>Sydney, by a fairly circuitous route.
I'll be posting this years sometime next week ....
Must have been cavorting in some sort of weird spacetime.
>You might tell the dissolute Oz Jr. that my friend the Ukrainian
>quantum gravity whiz Kirill Krasnov has gotten a position at
>Nottingham, where he'll be working with my friend John Barrett.
I very much doubt that such godlike figures would even notice such a
lowly organism as my son. If they only give morning lectures (for some
value of early) then they may never even see him. He did however manage
to pass all of the third semester exams, if you include one 'soft fail'
(electromagnetism!) as a pass. Actually he did well in the maths papers,
just the physics stuff let him down so I malign him. Given he only spent
36 hrs revising QM and 24 on EM (and missed most of the lectures) this
is hardly surprising. He claims to be working harder now, apparently if
he can scrape a 2.1 (not at all impossible) then he should be able to do
a MSc, which gives him another year being a dissolute student, which he
finds tempting.
I add this just to remind the assorted deities who read here that (and
they will find this astonishing) many undergraduates do not work as hard
as they should. Consequently they may only have a hazy understanding of
topics, or even no understanding at all. This explains the unanswered or
bizarre answers to exam questions. Hmmm, come to think of it most of my
answers to questions here are bizarre, so I probably haven't a leg to
stand on either.
[Oz jumps around having shot himself in the foot, again]
Charles Francis
> Third, there is no scientific, reductionistic alternative to many-
> worlds. All the other theories fail for logical reasons. (See "Is
> there any alternative theory?")
Any claim that the orthodox interpretation of quantum mechanics fails
for logical reasons is quite false. One may say, as did Einstein, that
qm does not give a complete picture of the quantum world, but not that
there is any inconsistency in Dirac-Von Neumann.
Regards
--
Charles Francis
John Baez
>John Baez <ba...@galaxy.ucr.edu> writes
>>You only need a tiny bit of math to follow this example:
>>for example, you need to know that the cosine of 60 degrees
>>is 1/2, and you need to know how to add and multiply fractions.
>I ought to be able to follow that, then. However I was hoping for an
>example, or at least illustration, using my particles coupled by a rigid
>rod.
That's basically what that website does. It shows the statistical
data you get from measuring spins of pairs of entangled spin-1/2
particles act in a way that can't possibly be matched by any
random ensemble of little arrows coupled by rigid bars.
But you may be after something even simpler.
>>PS - By the way, your Christmas card finally reached me here in
>>Sydney, by a fairly circuitous route.
>I'll be posting this years sometime next week ....
>Must have been cavorting in some sort of weird spacetime.
What?! It was the one with the cartoon about the turkey
calling up "the Zippo liposuction clinic". You're saying that
has been wandering about the planet for over a year???
>>You might tell the dissolute Oz Jr. that my friend the Ukrainian
>>quantum gravity whiz Kirill Krasnov has gotten a position at
>>Nottingham, where he'll be working with my friend John Barrett.
>I very much doubt that such godlike figures would even notice such a
>lowly organism as my son.
But he might notice them.
Btw, does your son know he gets discussed in this way in front
of a world-wide audience of physicists?
Daniel Davis
Ilja Schmelzer <schm...@wias-berlin.de> wrote:
> buybuyd...@yahoo.com (Daniel Davis) writes:
> > Ilja Schmelzer <schm...@wias-berlin.de> wrote:
> >> www.ilja-schmelzer.de/realism/game.html may be helpful.
I looked at it. The first perculiar thing I found was:
###
Is the game fair? If you simply use a "probability strategy" with
probability 1/3 for each statement, your chance to find a false
statement is at least one-third (at least because there may be also
three false statements).
###
I assume that you're not dealing with a normal 52 card deck - your 3
cards are selected with resampling, so that each card has an
independent probability of 1/2 of being black/red.
A larger issue is that the assumption of p=3D1/3 for any particular
statement is wrong: the probability is 1/2. We must be losing
something in the translation here.
###
Thus, our previous argumentation that the game is fair is already a
proof of Bell's inequality.
###
But this is the real problem. A discussion of a card game is not proof
of anything about QM. You can claim that the card game is in some way
analogous to QM, but that skips over the relevant issue separating
Bell and Jaynes: are Bell's assumptions valid in deriving his
inequality for local hidden variable theories for QM. Proof by analogy
will be meaningless, because there is not an agreement over the proper
probabilistic model of local hidden variable models for QM in the
first place.
> AFAIR Bell's original article (reprinted in "Speakable and
> Unspeakable") is a good place. Anyway this book is highly recommended
> reading.
Someone else recommended it as well. Out of print, according to
Amazon.
> Now, pointing out in general terms that correlation is not causation
> (this is what I see in Jaynes) as well as questioning the independence
> of the free decisions of the experimenters are argumentations of this
> type.
Jaynes would not question the independence of the decisions of the
experimenters, but this does not commit him to acceptance of the
independence of the *results* of those choices.
So Jaynes would go along with
P(ab|C) =3D P(a|C)P(b|C)
for certain C, but this would not commit him to=20
P(AB|abL) =3D P(A|aL)P(B|bL)
which Bell uses to derive his inequality as applicable to local hidden
variables theories.
This is a recurring theme I find in discussions with supporters of
Bell: variables are called independent without reference to
probability distributions or the information they are conditioned on,
and the claim of independence is "proved" by showing a lack of direct
causation. These are exactly the errors that Jaynes points out. The
other error I find is glossing over the actual point of contention
between Bell and Jaynes.
The point under contention between Jaynes and Bell is whether Bell's
proof really does exclude all local hidden variable theories. The
first point of disagreement is whether Bell's factorization is
justified: P(AB|abL) = P(A|aL)P(B|bL).
Then the rest of the derivation of the inequalities needs to be
justified (I think that will be less of a problem.) Then Bell needs to
show that the foregoing derivation applies equally to local hidden
variable theories with time variation.
Squark
> ...
> The first person to come up with one was Bell, and this
> is precisely why he's so famous - it's quite ingenious.
> Later various people came up with simplified examples.
> Unfortunately they all take a little bit of work to explain.
> Fortunately, I don't have to do this work, since Gary Felder
> already did:
>
> http://www2.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/bell.html
>
> This one is based on an example by Mermin.
I read it, but there must be something I'm missing. What he
basically says is that the probability of measuring the two
electrons to have opposite components of spin along two directions
randomly chosen from {x, y, z} (i.e. each direction is chosen
separately randomy with a probability of 1/3 for each choice) is
at least 5/9 in the hidden variables scenario (Bell inequality),
which is not hard to see, but it is 1/2 in real life. However, it
appears to mean in quantum mechanics it should be 2/3.
Lets see: in case the two chosen directions coincide the
probability of opposite outcomes is 1, due to the nature of the
considered quantum state (|up down> - |down up>, the spin 0 state).
In case the two directions are different, the probability appears
to be 1/2. This is because performing a measurement on the first
electron disentangles the system, resulting in the state |down up>
or |up down> (with respect to the corresponding axis). Now,
measuring the spin along a different axis on the other electron
gives the two possible outcomes with equal probability, as the
electron is in an eigenstate of our, orthogonal axis.
Summing up, we get 1 * 1/3 + 1/2 * 2/3 = 2/3. The 1/3 comes from
the fact the probability for the two chosen axes to coincide is
1/3. 2/3 > 5/9, so the Bell inequality isn't violated. Or is it?!
Best regards,
Squark
------------------------------------------------------------------
Write to me using the following e-mail:
Skvark_N...@excite.exe
(just spell the particle name correctly and change the
extension in the obvious way)
Oz
non-physics. -TB]
John Baez <ba...@galaxy.ucr.edu> writes
>>Oz:
>>I ought to be able to follow that, then. However I was hoping for an
>>example, or at least illustration, using my particles coupled by a rigid
>>rod.
>
>That's basically what that website does. It shows the statistical
>data you get from measuring spins of pairs of entangled spin-1/2
>particles act in a way that can't possibly be matched by any
>random ensemble of little arrows coupled by rigid bars.
>
>But you may be after something even simpler.
Yes. Where the two mechanisms differ. As I see it we are guaranteed to
find one spin-up if the other is measured spin-down. If it's more
complex than this, let me know.
>>>PS - By the way, your Christmas card finally reached me here in
>>>Sydney, by a fairly circuitous route.
>
>>I'll be posting this years sometime next week ....
>>Must have been cavorting in some sort of weird spacetime.
>
>What?! It was the one with the cartoon about the turkey
>calling up "the Zippo liposuction clinic". You're saying that
>has been wandering about the planet for over a year???
Nahhh, sent it at christmas.
I ought to post 2003 card now, to beat the spacetime warps surrounding
the wizard's castle.
>>I very much doubt that such godlike figures would even notice such a
>>lowly organism as my son.
>
>But he might notice them.
Only if they give lectures, he goes to their lectures, and is awake.
Three low probability events simultaneously.....
No, I malign him. He is starting to get interested, but has a LOT of
catching up to do. He has chosen one of the hardest courses offered by
UK universities, IMHO. He is capable of doing it quite well, when awake.
>Btw, does your son know he gets discussed in this way in front
>of a world-wide audience of physicists?
Only if he starts reading this group (which he should).
He could get a lot of excellent help here as he is well past my level,
although I still do manage to help him on occasion. Quite fun, actually.
I offer him up as an example undergraduate so as to inform the great and
good as to what some of their undergrads get up to/behave like. I think
this an important part of spr, because most if not all posters here will
teach and it's an important part of their job. You need to know your
enemy, to properly fight him ..... (sorry) ..... educate him.
My daughter, being the smartest of us, best grades, could have got into
any course except (perhaps) cambs maths and languages ....
chose economics .....
Smart cookie. The amount of *time* and brainpower required for sciences
is hugely greater than any other subject. Being an undergraduate is
about learning, but it's also about meeting people and getting some
lifetime friends. Oh, and a bit of having a good time, and why not?
Oz
>What's wrong with Oz's little model is not the impossibility of
>regarding spin in some such way, but his failure to include the
>effects of the measuring device configurations on the spins and on the
>measurement results -- in particular, the effects from the A-side
>device on the B-side spin, or vice versa.
OK. That's fine. So if I read between the lines correctly, what you are
saying is that the key is the effects on the A and B side measuring
equipment. That's reasonable.
Hmm what might be a good example?
Hmm, I'm going to say something that utterly exposes my huge ignorance
of spin, but that's good - I'll learn something.
For some reason I have got it into my head that polarisation (of
photons) is related to spin. This can't be right, though, because we
have the situation where particles can only be measured either spin-up
or spin-down whereas polarisation is up-down or left-right, and due to
the usually excessive numbers of photons behaves more like a vector that
can be rotated. Hmm, mind you that's probably true of spin (in bulk)
because a particle can presumably be some superposition (please insert
correct tech term) of spin until it's actually detected.
Oh, but we can have circularly polarised rotating clockwise and rotating
anticlockwise, which would look more like spin, I think. If so that will
be strongly related to u-d/l-r polarisations.
Anyway, pressing on regardless in typical Oz style and using coupled
polarised photons as a model to pick up the errors let's see how I would
see effects of polarisation on my little coupled spinning disk pair.
1) Coupled photons emitted at 90deg to each other.
2) Close to source whang both pairs through polarisers.
3) LHS is u-d, RHS is l-r.
4) Far away pass through 30deg polariser.
5) Quickly put through another 60 deg polariser.
6) Quickly detect results of pairs.
7) Correlate pairs.
Now I have a bit of a hangover and this doesn't look like having
anything odd about it so I'll see what the experts say about the
validity (or otherwise) of the experiment.
Ilja Schmelzer
> Ilja Schmelzer <schm...@wias-berlin.de> wrote:
>> buybuyd...@yahoo.com (Daniel Davis) writes:
>>> Ilja Schmelzer <schm...@wias-berlin.de> wrote:
>>>> www.ilja-schmelzer.de/realism/game.html may be helpful.
> I looked at it. The first perculiar thing I found was:
> ###
> Is the game fair? If you simply use a "probability strategy" with
> probability 1/3 for each statement, your chance to find a false
> statement is at least one-third (at least because there may be also
> three false statements).
> ###
>
> I assume that you're not dealing with a normal 52 card deck - your 3
> cards are selected with resampling, so that each card has an
> independent probability of 1/2 of being black/red.
>
> A larger issue is that the assumption of p=1/3 for any particular
> statement is wrong: the probability is 1/2. We must be losing
> something in the translation here.
Hm. Quite possible, I'm not a native speaker. "At least 1/3"
translates, AFAIU, as p >= 1/3. Thus, p=1/2 would be fine and not in
contradiction with my claim.
But we are not dealing with a 52 card deck with our without
resampling. We are dealing with an arbitrary unknown (hidden)
strategy of choosing the cards.
> ###
> Thus, our previous argumentation that the game is fair is already a
> proof of Bell's inequality.
> ###
> But this is the real problem. A discussion of a card game is not proof
> of anything about QM. You can claim that the card game is in some way
> analogous to QM, but that skips over the relevant issue separating
> Bell and Jaynes: are Bell's assumptions valid in deriving his
> inequality for local hidden variable theories for QM.
The argument is not an _analogy_ argument. The point is that you can
use the (ideal) QM device to win _this_ game, despite the _proof_ that
it is fair if there is no hidden information transfer.
> Proof by analogy will be meaningless, because there is not an
> agreement over the proper probabilistic model of local hidden
> variable models for QM in the first place.
Of course, the text was not written for the purpose of discussion Bell
vs. Jaynes.
But the question is: Would Jaynes accept that it is not possible to
win this game without hidden information transfer?
>> AFAIR Bell's original article (reprinted in "Speakable and
>> Unspeakable") is a good place. Anyway this book is highly
>> recommended reading.
> Someone else recommended it as well. Out of print, according to
> Amazon.
:-((((
>> Now, pointing out in general terms that correlation is not causation
>> (this is what I see in Jaynes) as well as questioning the independence
>> of the free decisions of the experimenters are argumentations of this
>> type.
> Jaynes would not question the independence of the decisions of the
> experimenters,
Yep. That's why I have written my statement in the form "X (this is
what I see in Jaynes) as well as Y have property Z".
Intended meaning: Y is not what I see in Jaynes, but also has property Z.
> The point under contention between Jaynes and Bell is whether Bell's
> proof really does exclude all local hidden variable theories. The
> first point of disagreement is whether Bell's factorization is
> justified: P(AB|abL) = P(A|aL)P(B|bL).
I have not found such a factorization in Bell's article.
> Then Bell needs to show that the foregoing derivation applies
> equally to local hidden variable theories with time variation.
I don't know any precise meaning of the phrase "hidden variable
theories with time variation".
eb...@lfa221051.richmond.edu
Squark <fii...@yahoo.com> wrote:
>ba...@galaxy.ucr.edu (John Baez) wrote in message
news:<b2n5sr$gla$1...@glue.ucr.edu>...
>> http://www2.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/bell.html
>>
>> This one is based on an example by Mermin.
>I read it, but there must be something I'm missing. What he
>basically says is that the probability of measuring the two
>electrons to have opposite components of spin along two directions
>randomly chosen from {x, y, z} (i.e. each direction is chosen
>separately randomy with a probability of 1/3 for each choice) is
>at least 5/9 in the hidden variables scenario (Bell inequality),
>which is not hard to see, but it is 1/2 in real life. However, it
>appears to mean in quantum mechanics it should be 2/3.
I think you're misinterpreting the experiment. The three directions
are not x,y,z; they're three equally-spaced directions in the xy plane
(120 degrees apart). Look at Appendix 3, down near the bottom of the
page.
It looks to me like everything works out right.
-Ted
--
[E-mail me at na...@domain.edu, as opposed to na...@machine.domain.edu.]
Fizz Fann
> Indeed, if you could model quantum entanglement as you suggest,
> people wouldn't regard it as "spooky" and rant about it until
> their faces turn purple and they keel over frothing at the mouth.
I think I understand the argument about nonlocality, although I
must confess I still think of it as spooky (I'll try not to keel over
and froth at the mouth, though!). It seems to me, though, that
its not the entanglment itself that is spooky, but rather the
nonlocal event of "wavefunction collapse" which seems to
be responsible for altering the future behavior of the faraway
electron. Did I get it completely wrong?
One more question; in Gary Felder's article, he says that
"Spooky action at a distance is part of nature", and this
seems to be the one point on which almost everyone agrees,
although aparrently some people froth at the mouth. So those
people who are comfortable with this idea - that when I look
at my shoe, I affect events on Anderomeda - can tell me how
they (mentally) reconsile this with relativity.
I know that there's no way to send a definite message, because
of some technicality, but it might be the case that if I didn't
look at my shoe, different events would occur on Anderomeda,
and those different events would have different consequences,
including (if they have quantum physics there too) possibly
consequences in my own past, if my understanding of the
term "relativity of simultanity" is right, _and if_ all this nonlocality
stuff really works. I know I can't control any of these "consequences
of consequences" (well, to be honest, I dont really understand that
bit, but its not important), but somewhere it seems to me that there
needs to be some extra law that hasn't been mentioned yet,
to prevent those consequences in my past from taking my shoes
and causing a paradox! Uncontrollable consequnces is not the
same as no consequences is what I think I'm saying.
On the other hand, I've probably just confused myself too much,
so maybe a non-frother will clear it up for me.
Alex.
Charles Francis
<thephy...@yahoo.com> writes
>One more question; in Gary Felder's article, he says that
>"Spooky action at a distance is part of nature", and this
>seems to be the one point on which almost everyone agrees,
I don't agree, and indeed there is a long philosophical tradition of
relationalism going back to Descartes and Leibniz which asserts that
there is a big difference between the breakdown of classical locality
and action at a distance. Just as relativity tells us that you cannot
say something is moving unless you say it is moving relative to other
matter, so relationalism asserts that you cannot say where something is
unless you say where it is relative to other matter.
It transpires that the supposedly spooky action at a distance in qm
occurs in precisely the situations in which you cannot say where
something is relative to other matter. Far from being agreed on action
at a distance, in the mainstream, or orthodox, interpretation in the
absence of observation we cannot even talk about the location of a
particle, and if we cannot talk about location, we certainly cannot talk
of distance or action at a distance either.
Regards
--
Charles Francis