Sean Carroll's new book

[John Clark]

It seems that nearly everyone on the list has a strong opinion about Sean Carroll's new book, but has anyone other than me actually read it? 

John K Clark

[Philip Thrift]

On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark wrote:

It seems that nearly everyone on the list has a strong opinion about Sean Carroll's new book, but has anyone other than me actually read it? 

John K Clark

He has posted several excepts (images of pages from the book) on Twitter and this excerpt

https://lithub.com/if-you-existed-in-multiple-universes-how-would-you-act-in-this-one/

and it's nothing new that I can see.

#philipthrift

[John Clark]

In other words the answer to my question is a resounding NO.

John K Clark

 

[Philip Thrift]

Maybe enlighten the world: What specifically in the book makes Many Worlds compelling vs. the one-world alternatives? And if there is nothing in the Many Worlds approach that is really better than a one-world approach, why multiply worlds beyond necessity? And where does all the extra matter come from to keep branching off new worlds again and again?

Seems like there should be some simply stated answers to these questions.

@philipthrift

[John Clark]

On Wed, Sep 25, 2019 at 9:30 AM Philip Thrift <cloud...@gmail.com> wrote:

> What specifically in the book makes Many Worlds compelling vs. the one-world alternatives? And if there is nothing in the Many Worlds approach that is really better than a one-world approach, why multiply worlds beyond necessity? And where does all the extra matter come from to keep branching off new worlds again and again?

Read the goddamn book and find out!

 John K Clark

[Philip Thrift]

NO!

I'm afraid of losing brain matter which might be needed to make a new(World).

@philipthrift 

[spudb...@aol.com]

I have it on my Kindle but have not read it yet because of a bad back and going to work (nights) so I have pushed the reading of Dr. Carroll way up Maslow's Hierarchy of Needs. I will get to it. 

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[smitra]

On 25-09-2019 15:30, Philip Thrift wrote:
> On Wednesday, September 25, 2019 at 8:15:59 AM UTC-5, John Clark
> wrote:
>
>> On Wed, Sep 25, 2019 at 9:11 AM Philip Thrift <cloud...@gmail.com>
>> wrote:
>>
>> On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark
>> wrote:
>>
>> It seems that nearly everyone on the list has a strong opinion about
>> Sean Carroll's new book, but has anyone other than me actually read
>> it?
>>
>> John K Clark
>>

>> _> He has posted several excepts (images of pages from the book) on
>> Twitter and this excerpt_
>>
>>
> https://lithub.com/if-you-existed-in-multiple-universes-how-would-you-act-in-this-one/
>> [1]
>>
>> _and it's nothing new that I can see._

>
> In other words the answer to my question is a resounding NO.
>
> John K Clark
>
> Maybe enlighten the world: What specifically in the book makes Many
> Worlds compelling vs. the one-world alternatives? And if there is
> nothing in the Many Worlds approach that is really better than a
> one-world approach, why multiply worlds beyond necessity? And where
> does all the extra matter come from to keep branching off new worlds
> again and again?
>
> Seems like there should be some simply stated answers to these
> questions.

I haven't read the book (yet) either, but the argument put forward by
Sean Carroll, Max Tegmark, David Deutsch, Lev Vaidman and many others
over the years, boils down to:

1) There is no hint from experiments of a violation of unitary time
evolution according to the Schrodinger equation.

2) People, equipment used to do measurements etc. consist of atoms that
are subject to the same laws of physics as everything else in the
universe.

3) Due to locality of interactions, the evolution of the physical state
of a system comprising of people, measurement apparatus and whatever is
measured, will be the same whether or not there would be a boundary
located at a distance of c T such that the interior would be perfectly
isolated from the exertion, making the interior a perfectly isolated
system.

Saibal

[Brent Meeker]

Except every measurement ever made in every experiment ever run.

>
> 2) People, equipment used to do measurements etc. consist of atoms
> that are subject to the same laws of physics as everything else in the
> universe.

Suppose, although I agree is hasn't been done, it could be shown that QM
predicts evolution into a mixed state.  Wouldn't that show that is
simply a probabilistic theory and it predicts probabilities and events
occur in accordance with those probabilities (as Omnes' writes).

Brent

[smitra]

Measurement involves an interaction of the system with another system.
But we can do measurements to verify whether or not the system itself
when it is perfectly isolated evolves according to the Schrodinger
equation. No violation has ever been found.

>


>>
>> 2) People, equipment used to do measurements etc. consist of atoms
>> that are subject to the same laws of physics as everything else in the
>> universe.
>
> Suppose, although I agree is hasn't been done, it could be shown that
> QM predicts evolution into a mixed state.  Wouldn't that show that is
> simply a probabilistic theory and it predicts probabilities and events
> occur in accordance with those probabilities (as Omnes' writes).

Even a mixed state can be interpreted as a multiverse. But you could
then argue that the separate worlds are totally independent of each
other and that then gives room for a theory that says that only one of
the worlds is real. Because in QM you never get this situation, that's
strong evidence for the reality of the different worlds.

Saibal

[Brent Meeker]

Of course not. They would have to be found by measurement...which
requires the realization of a single world.

>>
>
>
>>>
>>> 2) People, equipment used to do measurements etc. consist of atoms
>>> that are subject to the same laws of physics as everything else in
>>> the universe.
>>
>> Suppose, although I agree is hasn't been done, it could be shown that
>> QM predicts evolution into a mixed state.  Wouldn't that show that is
>> simply a probabilistic theory and it predicts probabilities and events
>> occur in accordance with those probabilities (as Omnes' writes).
>
> Even a mixed state can be interpreted as a multiverse. But you could
> then argue that the separate worlds are totally independent of each
> other and that then gives room for a theory that says that only one of
> the worlds is real. Because in QM you never get this situation, that's
> strong evidence for the reality of the different worlds.

You can't cite a theory that says multiple worlds exist as evidence for
multiple worlds exist.  That's strictly circular.  What I'm questioning
is whether QM is correct.  Zurek makes and argument that I think, if
worked out, would make the density matrix strictly diagonal.

Brent

[Lawrence Crowell]

On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark wrote:

It seems that nearly everyone on the list has a strong opinion about Sean Carroll's new book, but has anyone other than me actually read it? 

John K Clark

I have not read his book, but I have read his papers and the one he coauthored with Sebbens. I know what he has done. I am definitely agnostic about MWI as I am with all interpretations. Carroll and Sebens has though opened the door to a relationship between the Born rule and MWI, and I suspect quantum interpretations in general. Now that is something I find potentially very interesting.

LC 

[Bruce Kellett]

Have you seen Adrian Kent's critique of the Carroll-Sebens paper?

http://arxiv.org/abs/1408.1944

Bruce 

[Brent Meeker]

On 9/26/2019 5:01 PM, Lawrence Crowell wrote:

On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark wrote:

It seems that nearly everyone on the list has a strong opinion about Sean Carroll's new book, but has anyone other than me actually read it? 

John K Clark

I have not read his book, but I have read his papers and the one he coauthored with Sebbens. I know what he has done. I am definitely agnostic about MWI as I am with all interpretations. Carroll and Sebens has though opened the door to a relationship between the Born rule and MWI,

Didn't you read Quantum Theory of the Classical: Quantum Jumps, Born’s Rule, and Objective Classical Reality via Quantum Darwinism by Zurek.  arXiv:1807.02092v1 [quant-ph] 5 Jul 2018

He derives the Born rule from what he calls "environment induced supersymmetry".

Emergence of the classical world from the quantum substrate of our Universe is a long-standing
conundrum. I describe three insights into the transition from quantum to classical that are based
on the recognition of the role of the environment. I begin with derivation of preferred sets of states
that help define what exists - our everyday classical reality. They emerge as a result of breaking of
the unitary symmetry of the Hilbert space which happens when the unitarity of quantum evolutions
encounters nonlinearities inherent in the process of amplification – of replicating information. This
derivation is accomplished without the usual tools of decoherence, and accounts for the appearance
of quantum jumps and emergence of preferred pointer states consistent with those obtained via
environment-induced superselection, or einselection. Pointer states obtained this way determine
what can happen – define events – without appealing to Born’s rule for probabilities. Therefore, p k =
|ψ k | 2 can be now deduced from the entanglement-assisted invariance, or envariance – a symmetry of
entangled quantum states. With probabilities at hand one also gains new insights into foundations
of quantum statistical physics. Moreover, one can now analyze information flows responsible for
decoherence. These information flows explain how perception of objective classical reality arises from
the quantum substrate: Effective amplification they represent accounts for the objective existence
of the einselected states of macroscopic quantum systems through the redundancy of pointer state
records in their environment – through quantum Darwinism.

Brent

and I suspect quantum interpretations in general. Now that is something I find potentially very interesting.

LC 

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[spudb...@aol.com]

I still haven't read Carroll's book I downloaded because it's more intellectually enervating to view this argument. Beyond this, let us do a Useless Straw Poll here. If you were forced to choose the shape of reality, between 3 options, which one would you choose?

1)One Universe, 42 or 78 billion light years in extent, no next door neighbors.

2) The Multiverse. Could be MWI, could be Chaotic Inflation, could be subdomains, could be Tegmark's levels..?

3) One super-giant...Infinite Cosmos

Preferences? Why? Lower tax rates? Low crime rate? Keep out the Riff-raff? 

https://groups.google.com/d/msgid/everything-list/7f127b54-7897-591d-87e7-42bda87e2234%40verizon.net

.

[Bruce Kellett]

That paper, and others by Zurek, are the main reason I think that QM might ultimately make sense. Zurek understands that entanglement with the environment leads to essential non-unitary states. He concludes the above paper with:

"Everett's insight -- the realisation that relative states settle the problem of collapse -- was the key to these developments. But it is important to be careful in specifying what exactly we need from Everett and his followers, and what can be left behind. There is no doubt that the concept of relative states is crucial. Perhaps even more important is the idea that one can apply quantum theory to anything -- that there is nothing \ab initio\ classical. But the combination of these two ideas does not yet force one to adopt a "Many Worlds Interpretation" in which all the branches are equally real."

Bruce

[Brent Meeker]

I didn't find much force in Kent's criticism that it doesn't make sense for the observer to be split before he observes the result(s).  According to decoherence the whole environment is split in nano seconds by entanglement with the instrument...so why not the observer.  Then his observation is an essentially classical interaction with the instrument that changes the configuration of  his brain that produces the correlated conscious belief.

Brent

Bruce 

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[Bruce Kellett]

On Fri, Sep 27, 2019 at 11:05 AM 'Brent Meeker' via Everything List <everyth...@googlegroups.com> wrote:

On 9/26/2019 5:16 PM, Bruce Kellett wrote:

On Fri, Sep 27, 2019 at 10:01 AM Lawrence Crowell <goldenfield...@gmail.com> wrote:

On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark wrote:

It seems that nearly everyone on the list has a strong opinion about Sean Carroll's new book, but has anyone other than me actually read it? 

John K Clark

I have not read his book, but I have read his papers and the one he coauthored with Sebbens. I know what he has done. I am definitely agnostic about MWI as I am with all interpretations. Carroll and Sebens has though opened the door to a relationship between the Born rule and MWI, and I suspect quantum interpretations in general. Now that is something I find potentially very interesting.

Have you seen Adrian Kent's critique of the Carroll-Sebens paper?

http://arxiv.org/abs/1408.1944

I didn't find much force in Kent's criticism that it doesn't make sense for the observer to be split before he observes the result(s).  According to decoherence the whole environment is split in nano seconds by entanglement with the instrument...so why not the observer.  Then his observation is an essentially classical interaction with the instrument that changes the configuration of  his brain that produces the correlated conscious belief.

 

Yes, bu Carroll's argument depends on the observer's self-location uncertainty in the split second between the interaction and the decoherence stream reaching him, or his consciousness. I don't really like the idea that Carrol re-introduces the observer in an essential way into a theory that is supposed to get rid of all reference to observers.

Bruce

[Brent Meeker]

Zurek cites this paper by Haliwell where he writes:

https://arxiv.org/pdf/quant-ph/9902008.pdf

In this paper we have effectively shown that the decoherence condition is a reflection of the information
storage capacity of the environment. That is, it is a lower limit on the degree to which the histories may be fine-grained without the information storage capacity of the environment being exceeded.

But I don't see how to use this limit on information to prune the MWI branches.

Brent

Bruce

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[Bruce Kellett]

I don't even know what this means!

Decoherence goes on by unitary evolution, regardless of whether the environment can store the information or not. Decoherence has nothing to do with fine graining, or anything else we do. That is one of my main problems with the decoherent histories idea. It relies on this idea of fine or coarse graining, so it introduces the observer back into places where the observer must be irrelevant. I don't think Zurek's reference to Halliwell particularly endorses the decoherent histories approach. He says: "Previous studies of the records 'kept' by the environment were focussed on its effect on the state of the system, and not on their utility." So Halliwell's focus is orthogonal to the idea of quantum Darwinism.

Bruce

[Philip Thrift]

See if Sean Carroll answers the question of "weighing" worlds:

 

How much is too Many Worlds, is it just right?

https://groups.google.com/d/msg/everything-list/E3WLUdnW8jI/MLPg3dAhAgAJ

Suppose world W branches (in reality, not in "bookkeeping") to worlds W0 and W1.

If reality is pure information (basically purely mathematical bits of 0s and 1s), then that sort of "production" seems OK.

But what if W is (or contains) matter. Based on matter contents of W, W0, and W1:

If the matter contents of W0 plus W1 combined is greater than the matter content of W, how was the extra matter "produced"?

Two answers so far:

1. If an infinity of indiscernible universes already exist at the start and are only differentiating/diverging (instead of splitting), then no matter is created, all of it was already there.

2. Differentiation rather that duplication of matter is one possibility, but duplication of matter is not logically impossible either. Empirically, we have that matter cannot be created, but that is within a single world.

@philipthrift

 

[Quentin Anciaux]

And you forgot 3- it's always the same matter in w0 and w1, just seen from another POV, like a circle in a 2d plane could be thought to be from a sphere or a cylinder intersecting a 2d plane, so if you see the many 2d planes intersecting the cylinder, they see each a part of it, no new circle are created on each plane.

Quentin

 

@philipthrift

 

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[Philip Thrift]

On Friday, September 27, 2019 at 2:01:45 AM UTC-5, Quentin Anciaux wrote:

Le ven. 27 sept. 2019 à 08:41, Philip Thrift <cloud...@gmail.com> a écrit :

On Thursday, September 26, 2019 at 7:01:19 PM UTC-5, Lawrence Crowell wrote:

On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark wrote:

It seems that nearly everyone on the list has a strong opinion about Sean Carroll's new book, but has anyone other than me actually read it? 

John K Clark

I have not read his book, but I have read his papers and the one he coauthored with Sebbens. I know what he has done. I am definitely agnostic about MWI as I am with all interpretations. Carroll and Sebens has though opened the door to a relationship between the Born rule and MWI, and I suspect quantum interpretations in general. Now that is something I find potentially very interesting.

LC 

 

See if Sean Carroll answers the question of "weighing" worlds:

 

How much is too Many Worlds, is it just right?

https://groups.google.com/d/msg/everything-list/E3WLUdnW8jI/MLPg3dAhAgAJ

Suppose world W branches (in reality, not in "bookkeeping") to worlds W0 and W1.

If reality is pure information (basically purely mathematical bits of 0s and 1s), then that sort of "production" seems OK.

But what if W is (or contains) matter. Based on matter contents of W, W0, and W1:

If the matter contents of W0 plus W1 combined is greater than the matter content of W, how was the extra matter "produced"?

Two answers so far:

1. If an infinity of indiscernible universes already exist at the start and are only differentiating/diverging (instead of splitting), then no matter is created, all of it was already there.

2. Differentiation rather that duplication of matter is one possibility, but duplication of matter is not logically impossible either. Empirically, we have that matter cannot be created, but that is within a single world.

And you forgot 3- it's always the same matter in w0 and w1, just seen from another POV, like a circle in a 2d plane could be thought to be from a sphere or a cylinder intersecting a 2d plane, so if you see the many 2d planes intersecting the cylinder, they see each a part of it, no new circle are created on each plane.

Quentin

 

Sorry I missed it. This is the first I've read that answer.

Keep them coming!

BTW Sabine Hossenfelder just posted her Many Worlds view:

http://backreaction.blogspot.com/2019/09/the-trouble-with-many-worlds.html

@philipthrift

 

[Bruce Kellett]

On Fri, Sep 27, 2019 at 5:01 PM Quentin Anciaux <allc...@gmail.com> wrote:

And you forgot 3- it's always the same matter in w0 and w1, just seen from another POV, like a circle in a 2d plane could be thought to be from a sphere or a cylinder intersecting a 2d plane, so if you see the many 2d planes intersecting the cylinder, they see each a part of it, no new circle are created on each plane.

That seems similar to the view of Chad Orzel:

https://scienceblogs.com/principles/2008/11/20/manyworlds-and-decoherence

His idea is that there aren't many worlds, just the wave function of the universe. So there is no splitting and no multiplication of worlds, there is just the wave function. And our world is just our path through this wave function. This is, therefore, a single world interpretation since we see only one world. The other parts of the wave function may exist, but they are not worlds like ours.

Bruce

[Philip Thrift]

Philip Ball talks about Hossenfelder's take, then Orzel's take:

https://philipball.blogspot.com/2019/09/just-how-conceptually-economical-is.html :

...

Sabine Hossenfelder: "Many Worlds in and by itself doesn't say anything about whether the parallel worlds "exist" because no theory ever does that. We infer that something exists - in the scientific sense - from observation. It's a trivial consequence of this that the other worlds do not exist in the scientific sense. You can postulate them into existence, but that's an *additional* assumption. As I have pointed out before, saying that they don't exist is likewise an additional assumption that scientists shouldn't make. The bottom line is, you can believe in these worlds the same way that you can believe in God.”

I have some sympathy with this, but I think I can imagine the Everettian response, which is to say that in science we infer all kinds of things that we can’t observe directly, because of their indirect effects that we can observe. The idea then is that the Many Worlds are inescapably implicit in the Schrödinger equation, and so we are compelled to accept them if we observe that the Schrödinger equation works. The only way we’d not be obliged to accept them is if we had some theory that erases them from the equation. There are various arguments to be had about that line of reasoning, but I think perhaps the most compelling is that there are no other worlds explicitly in any wavefunction ever written. They are simply an interpretation laid on top. Another, equally tenable, interpretation is that the wavefunction enumerates possible outcomes of measurement, and is silent about ontology. In this regard, I totally agree with Sabine: nothing compels us to believe in Many Worlds, and it is not clear how anything could ever compel us.

In fact, Chad Orzel suggests that the right way to look at the MWI might be as a mathematical formalism that makes no claims about reality consisting of multiple worlds – a kind of quantum book-keeping exercise, a bit like the path integrals of QED. I’m not quite sure what then is gained by looking at it this way relative to the standard quantum formalism – or indeed how it then differs at all – but I could probably accept that view. Certainly, there are situations where one interpretational model can be more useful than others. However, we have to recognize that many advocates of Many Worlds will have none of that sort of thing; they insist on multiple separate universes, multiple copies of “you” and all the rest of it – because their arguments positively require all that.

Here, then, is the key point: you are not obliged to accept the “other worlds” of the MWI, but I believe you are obliged to reject its claims to economy of postulates. Anything can look simple and elegant if you sweep all the complications under the rug.

@philipthrift 

[Alan Grayson]

But if every interaction with the environment in decoherence satisfies unitary time evolution, how can the result deny unitary time evolution? AG 

[Bruce Kellett]

On Fri, Sep 27, 2019 at 8:38 PM Alan Grayson <agrays...@gmail.com> wrote:

On Wednesday, September 25, 2019 at 6:56:31 PM UTC-6, Brent wrote:

Except every measurement ever made in every experiment ever run.

But if every interaction with the environment in decoherence satisfies unitary time evolution, how can the result deny unitary time evolution? AG 

Every measurement ever made gave only one result. This means that unitarity is violated in giving that single result rather than a superposition. Understanding the reason for this might require some more work.

Bruce 

[Alan Grayson]

If you've done that work and are convinced that unitary time evolution is violated when a measurement occurs, is this tantamount to claiming that the wf collapses? AG  

[Lawrence Crowell]

I have only been able to read a bit into this. It is on an open tab that I keep. I do intend to give this a pretty thorough reading in the near future. I need to have more clarity in what is meant by supersymmetry here.

LC

 

and I suspect quantum interpretations in general. Now that is something I find potentially very interesting.

LC 

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[Bruce Kellett]

I don't claim to have done the work to show how this happens. But collapse is one possibility.

Bruce 

[Alan Grayson]

You infer that unitary time evolution would be maintained in a measurement if we got all possible results. This seem hugely implausible since it would mean a single source particle would result in many hits on the screen, possibly countable or uncountable. AG  

[Bruno Marchal]

On 27 Sep 2019, at 02:50, spudboy100 via Everything List <everyth...@googlegroups.com> wrote:

I still haven't read Carroll's book I downloaded because it's more intellectually enervating to view this argument. Beyond this, let us do a Useless Straw Poll here. If you were forced to choose the shape of reality, between 3 options, which one would you choose?

1)One Universe, 42 or 78 billion light years in extent, no next door neighbors.

2) The Multiverse. Could be MWI, could be Chaotic Inflation, could be subdomains, could be Tegmark's levels..?

3) One super-giant...Infinite Cosmos

Preferences? Why? Lower tax rates? Low crime rate? Keep out the Riff-raff? 

You forget

4) zero universe

“4)” is logically implied by Mechanism (used by Darwin, and unfortunately (for them) materialist (making them inconsistent);

All you need to understand is what is a computation. Then it is simple to show that all computations exists, and have a very complex subtle redundancy structured by the universal machine themselves in arithmetic.

And that explains the appearance of a quantum multiverse, assuming 0 (physical) universe. 

Bruno

To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/1630383382.13201426.1569545435228%40mail.yahoo.com.

[Bruno Marchal]

On 27 Sep 2019, at 02:34, 'Brent Meeker' via Everything List <everyth...@googlegroups.com> wrote:

On 9/26/2019 5:01 PM, Lawrence Crowell wrote:

On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark wrote:

It seems that nearly everyone on the list has a strong opinion about Sean Carroll's new book, but has anyone other than me actually read it? 

John K Clark

I have not read his book, but I have read his papers and the one he coauthored with Sebbens. I know what he has done. I am definitely agnostic about MWI as I am with all interpretations. Carroll and Sebens has though opened the door to a relationship between the Born rule and MWI,

Didn't you read Quantum Theory of the Classical: Quantum Jumps, Born’s Rule, and Objective Classical Reality via Quantum Darwinism by Zurek.  arXiv:1807.02092v1 [quant-ph] 5 Jul 2018

He derives the Born rule from what he calls "environment induced supersymmetry".

Emergence of the classical world from the quantum substrate of our Universe is a long-standing
conundrum. I describe three insights into the transition from quantum to classical that are based
on the recognition of the role of the environment. I begin with derivation of preferred sets of states
that help define what exists - our everyday classical reality. They emerge as a result of breaking of
the unitary symmetry of the Hilbert space which happens when the unitarity of quantum evolutions
encounters nonlinearities inherent in the process of amplification – of replicating information.

This use mechanism, and give the MW, and explain QM and the classical worlds appearances from it.

But that makes sense only if the SWE is extracted from arithmetic, or they will remain some magic.

Bruno

This
derivation is accomplished without the usual tools of decoherence, and accounts for the appearance
of quantum jumps and emergence of preferred pointer states consistent with those obtained via
environment-induced superselection, or einselection. Pointer states obtained this way determine
what can happen – define events – without appealing to Born’s rule for probabilities. Therefore, p k =
|ψ k | 2 can be now deduced from the entanglement-assisted invariance, or envariance – a symmetry of
entangled quantum states. With probabilities at hand one also gains new insights into foundations
of quantum statistical physics. Moreover, one can now analyze information flows responsible for
decoherence. These information flows explain how perception of objective classical reality arises from
the quantum substrate: Effective amplification they represent accounts for the objective existence
of the einselected states of macroscopic quantum systems through the redundancy of pointer state
records in their environment – through quantum Darwinism.

Brent

and I suspect quantum interpretations in general. Now that is something I find potentially very interesting.

LC 

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[Bruno Marchal]

See my answer to spudboy. There is no matter, and 0 physical universe, just the computations emulated by the +/* structure of arithmetic; that is, all computations. That include the quantum one, but that does not explain the quantum one. To explain them, we have to prove that only them win the first indeterminacy problem in arithmetic (or there will be an appel to something non Turing emulable or first person recoverable.

But even with quantum mechanics, that problem can be solved, as the laws are statistical, and the universe never interact. Linearity precludes us to steal the oil in a parallel universe. Amazingly, if QM was not 100% linear (if the wave equation was only the first term of some series) we would be able to interact in between universe, but thermodynamic would get wrong, relativity would become wrong, well, nobody try this anymore.

Bruno

 

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[Bruno Marchal]

On 27 Sep 2019, at 09:56, Bruce Kellett <bhkel...@gmail.com> wrote:

On Fri, Sep 27, 2019 at 5:01 PM Quentin Anciaux <allc...@gmail.com> wrote:

And you forgot 3- it's always the same matter in w0 and w1, just seen from another POV, like a circle in a 2d plane could be thought to be from a sphere or a cylinder intersecting a 2d plane, so if you see the many 2d planes intersecting the cylinder, they see each a part of it, no new circle are created on each plane.

That seems similar to the view of Chad Orzel:

https://scienceblogs.com/principles/2008/11/20/manyworlds-and-decoherence

His idea is that there aren't many worlds, just the wave function of the universe. So there is no splitting and no multiplication of worlds, there is just the wave function.

That is Everett.

And our world is just our path through this wave function.

But too keep unitarity, that makes our path just a path among many paths.

This is, therefore, a single world interpretation since we see only one world.

That does not follow. The guy in Washington see only one city, but we know, and he knows that the guy in Moscow also see one city. The doppelgänger does not disappear in this case, nor in the universal wave of Everett. To say there is only one world because we see only one world is akin to a form of (cosmic) solipsisme.

The other parts of the wave function may exist, but they are not worlds like ours.

From our perspective, but from the observer perspective in the other worlds, it looks like ours. 

Bruno

Bruce

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[Bruno Marchal]

Good, you are on the right path. Indeed, we get uncountable hit (in classical QM) on the screen, but the SWE implies that when you look where the hit is, you only entangle yourself which the hit, so there will be uncountable many AG each saying, but the hit is unique, like the W guy says that he sees only Washington.

Bruno

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[smitra]

On 26-09-2019 21:38, 'Brent Meeker' via Everything List wrote:
> On 9/26/2019 11:55 AM, smitra wrote:

>> On 26-09-2019 02:56, 'Brent Meeker' via Everything List wrote:
>>> On 9/25/2019 2:28 PM, smitra wrote:

>>>> On 25-09-2019 15:30, Philip Thrift wrote:
>>>>> On Wednesday, September 25, 2019 at 8:15:59 AM UTC-5, John Clark

>>>>> wrote:
>>>>>
>>>>>> On Wed, Sep 25, 2019 at 9:11 AM Philip Thrift <cloud...@gmail.com>

>>>>>> wrote:
>>>>>>
>>>>>> On Wednesday, September 25, 2019 at 6:54:59 AM UTC-5, John Clark
>>>>>> wrote:
>>>>>>
>>>>>> It seems that nearly everyone on the list has a strong opinion
>>>>>> about
>>>>>> Sean Carroll's new book, but has anyone other than me actually
>>>>>> read
>>>>>> it?
>>>>>>
>>>>>> John K Clark
>>>>>>

>>>>>> _> He has posted several excepts (images of pages from the book)
>>>>>> on
>>>>>> Twitter and this excerpt_
>>>>>>
>>>>>>
>>>>> https://lithub.com/if-you-existed-in-multiple-universes-how-would-you-act-in-this-one/
>>>>>> [1]
>>>>>>
>>>>>> _and it's nothing new that I can see._
>>>>>
>>>>> In other words the answer to my question is a resounding NO.
>>>>>
>>>>> John K Clark
>>>>>
>>>>> Maybe enlighten the world: What specifically in the book makes Many
>>>>> Worlds compelling vs. the one-world alternatives? And if there is
>>>>> nothing in the Many Worlds approach that is really better than a
>>>>> one-world approach, why multiply worlds beyond necessity? And where
>>>>> does all the extra matter come from to keep branching off new
>>>>> worlds
>>>>> again and again?
>>>>>
>>>>> Seems like there should be some simply stated answers to these
>>>>> questions.
>>>>
>>>> I haven't read the book (yet) either, but the argument put forward
>>>> by Sean Carroll, Max Tegmark, David Deutsch, Lev Vaidman and many
>>>> others over the years, boils down to:
>>>>
>>>> 1) There is no hint from experiments of a violation of unitary time
>>>> evolution according to the Schrodinger equation.
>>>
>>

>>> Except every measurement ever made in every experiment ever run.
>>

>> Measurement involves an interaction of the system with another system.
>> But we can do measurements to verify whether or not the system itself
>> when it is perfectly isolated evolves according to the Schrodinger
>> equation. No violation has ever been found.
>
> Of course not. They would have to be found by measurement...which
> requires the realization of a single world.

That measurement effectively collapses the wavefunction doesn't prevent
one from performing experiments to verify that no collapse happens in
the absence of interactions with external degrees of freedom. One can
e.g. do experiments using a quantum computer, apply a unitary transform
to a qubit and then apply the inverse of that transform and then measure
the state of the qubit. If the qubit's state had collapsed or interacted
with the environment, then the final state would be different from the
initial state and that van be detected.

>
>>>
>>
>>
>>>>
>>>> 2) People, equipment used to do measurements etc. consist of atoms
>>>> that are subject to the same laws of physics as everything else in
>>>> the universe.
>>>
>>> Suppose, although I agree is hasn't been done, it could be shown that
>>> QM predicts evolution into a mixed state.  Wouldn't that show that is
>>> simply a probabilistic theory and it predicts probabilities and
>>> events
>>> occur in accordance with those probabilities (as Omnes' writes).
>>

>> Even a mixed state can be interpreted as a multiverse. But you could
>> then argue that the separate worlds are totally independent of each
>> other and that then gives room for a theory that says that only one of
>> the worlds is real. Because in QM you never get this situation, that's
>> strong evidence for the reality of the different worlds.
>
> You can't cite a theory that says multiple worlds exist as evidence
> for multiple worlds exist.  That's strictly circular.  What I'm
> questioning is whether QM is correct.  Zurek makes and argument that I
> think, if worked out, would make the density matrix strictly diagonal.
>

If you approximate the environment as consisting of an infinite number
of degrees of freedom, then the different branches can decohere exactly.
Zurek's "envirance" argument becomes exact in this limit of an infinite
number of degrees of freedom. But since interactions are local and there
are only a finite number of physical degrees of freedom involved in the
interactions in a finite time, one cannot appeal to an exact
decoherence.

Saibal

[Philip Thrift]

If There is no matter, and [whatever follows] -- if that is true -- then I am happy with anything the Many Worlders say is real, or anyone else's "interpretation" of reality. It doesn't matter :)  because then one is just talking about fiction, i.e. criticizing texts (what people write).

@philipthrift

[Brent Meeker]

The "new"  matter (and energy and space and information) are discounted by the probability of their existence. It seems curious to me that the MWI advocates want to take the wave function ontologically but not the Hilbert space.  From the viewpoint of Hilbert space all the different "worlds" are just subspaces on which the wave-function of the multiverse can be projected.  A world "splitting" is just the unfolding of a world into two orthogonal subspaces.

Brent

[Brent Meeker]

On 9/27/2019 2:40 AM, Philip Thrift wrote:

hilip Ball talks about Hossenfelder's take, then Orzel's take:

https://philipball.blogspot.com/2019/09/just-how-conceptually-economical-is.html :

...

Sabine Hossenfelder: "Many Worlds in and by itself doesn't say anything about whether the parallel worlds "exist" because no theory ever does that. We infer that something exists - in the scientific sense - from observation. It's a trivial consequence of this that the other worlds do not exist in the scientific sense. You can postulate them into existence, but that's an *additional* assumption. As I have pointed out before, saying that they don't exist is likewise an additional assumption that scientists shouldn't make. The bottom line is, you can believe in these worlds the same way that you can believe in God.”

I have some sympathy with this, but I think I can imagine the Everettian response, which is to say that in science we infer all kinds of things that we can’t observe directly, because of their indirect effects that we can observe. The idea then is that the Many Worlds are inescapably implicit in the Schrödinger equation, and so we are compelled to accept them if we observe that the Schrödinger equation works. The only way we’d not be obliged to accept them is if we had some theory that erases them from the equation. There are various arguments to be had about that line of reasoning, but I think perhaps the most compelling is that there are no other worlds explicitly in any wavefunction ever written. They are simply an interpretation laid on top. Another, equally tenable, interpretation is that the wavefunction enumerates possible outcomes of measurement, and is silent about ontology. In this regard, I totally agree with Sabine: nothing compels us to believe in Many Worlds, and it is not clear how anything could ever compel us.

In fact, Chad Orzel suggests that the right way to look at the MWI might be as a mathematical formalism that makes no claims about reality consisting of multiple worlds – a kind of quantum book-keeping exercise, a bit like the path integrals of QED.

Which is exactly the approach of QBism.

Brent

[Brent Meeker]

On 9/27/2019 3:38 AM, Alan Grayson wrote:

1) There is no hint from experiments of a violation of unitary time
> evolution according to the Schrodinger equation.

Except every measurement ever made in every experiment ever run.

But if every interaction with the environment in decoherence satisfies unitary time evolution, how can the result deny unitary time evolution? AG 

Because unitary evolution cannot convert a superposition to a mixture, much less to a single value.

Bent

[Brent Meeker]

"Collapse" is certainly the case if you take an epistemic view of the wave-function: measurment=>new information=>new wave function.

Brent

[Brent Meeker]

On 9/27/2019 12:35 AM, Philip Thrift wrote:

BTW Sabine Hossenfelder just posted her Many Worlds view:

http://backreaction.blogspot.com/2019/09/the-trouble-with-many-worlds.html

Sabine writes:

The reason is this. In the many worlds interpretation, if you set up a detector for a measurement, then the detector will also split into several universes. Therefore, if you just ask “what will the detector measure”, then the answer is “The detector will measure anything that’s possible with probability 1.”

This, of course, is not what we observe. We observe only one measurement outcome. The many worlds people explain this as follows. Of course you are not supposed to calculate the probability for each branch of the detector. Because when we say detector, we don’t mean all detector branches together. You should only evaluate the probability relative to the detector in one specific branch at a time.

That sounds reasonable. Indeed, it is reasonable. It is just as reasonable as the measurement postulate. In fact, it is logically entirely equivalent to the measurement postulate.

This turns on "we only observe one measurement outcome" and  this "...is logically equivalent to the measurement postulate"  But the MWI says that we observe all possible outcomes just as the detector measures all possible outcomes.  She seems to elide the observer splitting, and assumes there's a "soul" or "person" that doesn't split but instead goes to only one branch of the MW.

Brent

[Philip Thrift]

On QBism (What did quanta do before the "subjects" of subjective probability evolved?):

https://arxiv.org/abs/1409.3312

QBism: A Critical Appraisal

Ulrich Mohrhoff

(Submitted on 11 Sep 2014)

By insisting that the formal apparatus of quantum mechanics is a probability calculus, QBism opens the door to a deeper understanding of what quantum mechanics is trying to tell us. By insisting on a subjectivist Bayesian interpretation of probability in the context of quantum foundations, it closes this door again. To find the proper balance between subject and object, one must turn to Niels Bohr, the alleged "obscurity" of whose views casts a poor light on the current state of foundational research.

@philipthrift 

[Bruce Kellett]

On Fri, Sep 27, 2019 at 7:40 PM Philip Thrift <cloud...@gmail.com> wrote:

On Friday, September 27, 2019 at 2:56:42 AM UTC-5, Bruce wrote:

On Fri, Sep 27, 2019 at 5:01 PM Quentin Anciaux <allc...@gmail.com> wrote:

And you forgot 3- it's always the same matter in w0 and w1, just seen from another POV, like a circle in a 2d plane could be thought to be from a sphere or a cylinder intersecting a 2d plane, so if you see the many 2d planes intersecting the cylinder, they see each a part of it, no new circle are created on each plane.

That seems similar to the view of Chad Orzel:

https://scienceblogs.com/principles/2008/11/20/manyworlds-and-decoherence

His idea is that there aren't many worlds, just the wave function of the universe. So there is no splitting and no multiplication of worlds, there is just the wave function. And our world is just our path through this wave function. This is, therefore, a single world interpretation since we see only one world. The other parts of the wave function may exist, but they are not worlds like ours.

Bruce

Philip Ball talks about Hossenfelder's take, then Orzel's take:

https://philipball.blogspot.com/2019/09/just-how-conceptually-economical-is.html :

Ball's analysis is very much to the point -- there is no compelling evidence for many worlds and, despite the claims, Everettian approaches make just as many extra assumptions as other approaches -- they are just not as open about their additional assumptions/postulates.

"Here, then, is the key point: you are not obliged to accept the “other worlds” of the MWI, but I believe you are obliged to reject its claims to economy of postulates. Anything can look simple and elegant if you sweep all the complications under the rug." (Ball)

Bruce

[Philip Thrift]

via BackReAction (by @skdh):

http://backreaction.blogspot.com/2019/09/the-trouble-with-many-worlds.html?showComment=1569595660330#c5108725356973561367

Phillip Helbig 

"What is your explanation as to why many people who are obviously very smart like ... Sean Carroll, etc. subscribe to the many-worlds interpretation?"

Replies:

Sabine Hossenfelder

"I'm a physicist, not a psychologist."

@philipthrift

[Alan Grayson]

Brent

Not sure I understand. Do you mean that SINCE the system being measured is originally in a superposition, and finally becomes a mixture, it implies a denial of unitary time evolution? If so, how do you know that the final result is mixture? TIA, AG 

[Brent Meeker]

It's only a mixture that can be interpreted as a probability assignment.  Decoherence gets the reduced entropy matrix to a mixture FAPP...but not exactly, unless we add something new to the theory.

Brent

[Alan Grayson]

Are there any distinguishing features to these orthogonal subspaces? If we traveled to one of them, would we detect anything different or unusual from the space in which we previously resided? AG 

[Brent Meeker]

On 9/28/2019 3:42 PM, Alan Grayson wrote:

The "new"  matter (and energy and space and information) are discounted by the probability of their existence. It seems curious to me that the MWI advocates want to take the wave function ontologically but not the Hilbert space.  From the viewpoint of Hilbert space all the different "worlds" are just subspaces on which the wave-function of the multiverse can be projected.  A world "splitting" is just the unfolding of a world into two orthogonal subspaces.

Brent

Are there any distinguishing features to these orthogonal subspaces? If we traveled to one of them, would we detect anything different or unusual from the space in which we previously resided? AG 

You would notice that the quantum measurement you did had just resulted in UP (or DOWN).

Brent

[Philip Thrift]

When a bundle of histories combine (interfere, reinforce), only one survives.

All the other histories die, and go to the quantum netherworld.

@philipthrift 

[Bruno Marchal]

That is valid only if you define real by material. But if matter is not real, then, as no one doubt about the material appearances, it might mean that something else might be real, like 2+2 = 4 has to be real to be able to define what is a digital machine, just to name an example.

Bruno

@philipthrift

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[Bruno Marchal]

Exactly.

Bruno

Brent

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[Bruno Marchal]

Right, and that is the usual confusion between 1p and 3p, or between []p and []p & p. It is the W-guy saying to the journalist in Washington: “let us forget the M-guy” as we are not in Moscow.

Bruno

Brent

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