Discussion with Prof. Strassler on virtual particles

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Discussion with Prof. Strassler on virtual particles FrediFizzx 7/26/12 8:03 PM
Below is a discussion I was having with Prof. Strassler on,

http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/

My discussion starts here if this link works or scroll down near the bottom.

http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/#comment-14599

Seems he has turned off replies for the thread (censored me) so I will have
to reply to his last comments here (see near the end).  Apparently Prof.
Strassler is a bit touchy concerning his "disturbance" hypothesis.
-------------------------------------------
Fred D. | July 22, 2012 at 4:09 PM |

Hi Matt,

I am glad you think that virtual "particles" are real. There seems to be a
movement in some European circles that they are not real. For example, I got
booted off physicsforums.com for arguing that they are real and you can see
the link above to Arnold Neumaier's FAQ (a PF.com advisor). I sort of get
your drift that you want to call them disturbances but my particle physics
instructor, Dr. Andy Inopin, taught me that they have all the same exact
properties as their "real" counterparts except they are simply "off mass
shell" and can't be detected. Well.. of course if they are detected, they
become "real".

Take muon decay as an example. If there isn't a real virtual W boson
involved, the muon could never decay. That virtual W boson has all the same
properties as a "real" W boson except for it is "off mass shell". So your
"disturbance" here sure smells like a W boson particle. Now, I think that
with lower energy Coulomb type interactions, the "disturbance" connotation
could be appropriate. Perhaps you mentioned that above as I did not read all
of the preceding comments.

Best,

Fred
---------------------------------------------
Matt Strassler | July 23, 2012 at 3:28 PM |

You are putting huge numbers of words in my mouth here. Your example of the
W boson in the case of muon decay is exactly opposite to what I said. You
say "your disturbance sure smells like a W boson particle". Obviously you
have a serious problem with your nose. I said very specifically: "`virtual
particles' are NOT particles"; particles are resonances, virtual particles
are not. They can even have negative mass-squared (does this not bother
you?)

-----------------------------------
Fred D. | July 24, 2012 at 7:20 PM |

I know it is opposite of what you said. I suspect most particle physicists
would disagree with you about the example of muon decay with the virtual W
boson being just a "disturbance". I would think it is in fact a temporary
resonance that has all the properties of of a real W boson except for its
mass. So there is a possible counter-example to your "disturbance"
hypothesis. There are of course many others. In particle physics, the term
"virtual particle" has a very specific meaning. It simply means a particle
that is "off mass shell". Griffiths' says in "Intro. to Elementary
 Particles", "Actually, the _physical_ distinction between real and virtual
particles is not quite as sharp as I have implied. If a photon is emitted on
Alpha Centauri, and absorbed in your eye, it is technically a virtual
photon. However, in general, the farther a virtual particle is from its mass
shell the shorter it lives, so a photon from a distant star would have to be
extremely close to its 'correct' mass - it would have to be _almost_
'real'."

What is an example of a virtual particle that has "negative mass squared"? I
would suspect it may be related to momentum. Thanks.
-----------------------------------
Matt Strassler | July 25, 2012 at 10:51 AM |

PS:  Your suspicion is wrong. And the fact that you have never heard of a
virtual
particle with negative mass-squared puts a knife into your credibility.
[Check: what is the mass-squared of a photon exchanged between an electron
and a nucleus?]

FD:  All my particle physics text books have it as negative
momentum-squared.  I have no problem with that.  I searched quickly through
all of Weinberg's texts on Quantum Field Theory and also negative
momentum-squared there also.  But after a search of the iNet, it does seem
the term "negative mass-squared" is used also.

PS:  Go learn some quantum field theory, and don't bother me with irrelevant
statements [such as Griffiths' correct, but obvious, point] until you
understand the main difference between a propagator (which can have any mass
and a relatively arbitrary functional form) and a particle (which is a pole
in that propagator, has a definite mass [possibly with a non-zero width] and
is controlled by theorems that do not apply to the propagator.) The fact
that two things are continuously connected does not make them equal; yes,
the distinction between a virtual particle and a real particle is only sharp
if the particle has an infinite lifetime, and even then, there is a limit
you can take where one resembles the other (as in Griffiths' example) and
that's even critical in doing calculations; but no, that doesn't mean you
should view them as simply equivalent. And I'm trying to explain physics to
the public on this site, not to experts, for whom this subtlety would need
to be properly explored.

FD:  Sorry that you feel "bothered".  I didn't say they were equivalent.
How could they possibly be exactly the same if the virtual particle is "off
mass shell".  However, in all cases, the virtual particle does have all the
same properties as its "real" counterpart except for mass.

PS:  On the example of muon decay; let's take, instead, the scattering of an
electron off a positron to make a W+ and W-. There are three interfering
processes, one with a virtual photon of positive mass-squared, one with a
virtual Z of positive mass-squared, one with a virtual neutrino of negative
mass-squared. Are they all particles? Or are some more "particle" than
others? Oh, and that's only at lowest-order in the quantum field theory.
There are also processes where the electron and positron turn into multiple
virtual particles with all sorts of different mass-squareds that we have to
integrate over. Are these all to be thought of as particles, even though
within the integration the mass-squared will vary from negative across zero
to positive? And there are several interfering processes, while we're at it;
how are you thinking about these?

FD:  Strange that you asked all these questions then turned off reply on the
thread.  Yes, they are all particles; some more off mass shell than others.
But they all have the same properties as their real counterparts other than
mass.  The calculations for these processes would be impossible if their
properties were not the same.

PS:  It's a mistake to view these things as particles. A fundamental
mistake. The
W particle that appears in top quark decay is different from the W virtual
particle that appears in muon decay, or that allows a neutrino to scatter
off a nucleus and turn into an electron. The issue is the lifetime. A W
particle has a lifetime that corresponds to a width of about 2 GeV. A W
particle that is much further off-shell than 2 GeV decays away not because
of damping but because it is non-resonant; a W particle that is much less
off-shell than 2 GeV decays away due to damping, not due to being
off-resonance. Again, these are continuously connected, but so is a young
man and an old man; so are red and yellow; that does not make them
equivalent.

FD:  It is not a mistake to view them as "off mass shell" particles in the
case you are describing here.  And if you don't view them as particles with
the particular properties they have, you would never be able to calculate
anything.

PS:  I trained under Peskin, Susskind, Banks, Seiberg, Witten, Shenker, and
Wilczek, and my research in quantum field theory and my teaching of quantum
field theory's many subtleties is well-known. My readers don't need your
advice.

FD:  I have been intensely studying virtual particle for close to 10 years
now and though your readers may not need my advice, they might be interested
in my opinions on the subject.  We are well aware of your qualifications but
I don't think they are helping you much here with your "disturbance"
hypothesis.  At least as applied to *all* virtual particles.  Now as
mentioned previously, I do agree with calling Coulomb type interactions like
you describe in your web article "disturbances" rather than resorting to
virtual photons.  But it is totally wrong to explain to laypeople that they
should view all virtual particles as merely disturbances.  The actual real
problem is with the name "virtual" for a particle that is off mass shell.
But we are stuck with it now.

Let's take a look at the Coulomb interaction between two electrons as you
have in your article and I will give my hypothesis which I think is much
more transparent and an easy explanation.  The presence of an electron does
"disturb" the quantum "vacuum" but does so in a fairly regular way.  It
simply "tilts" virtual fermionic pairs surrounding it by attracting the
positive part of the pair toward it and repels the negative part.  This is
what makes the "static" electric and magnetic fields around the point charge
and it basically goes off to infinity but then there is the cluster
decomposition principle that limits that.  And since the virtual fermionic
pairs are bosons, they can interact with each other directly.  No virtual
photons needed at all in this case.  Well... of course there will be some
virtual photons involved here and there because nothing is perfectly static.
Just as there are no particles that are perfectly "on mass shell".  You can
always draw a bigger Feynman diagram where your so-called "on mass shell"
particles are internal lines in the diagram.

Best,

Fred Diether

 

Re: Discussion with Prof. Strassler on virtual particles robert bristow-johnson 7/26/12 9:07 PM
On 7/26/12 11:03 PM, FrediFizzx wrote:
>
>
> I am glad you think that virtual "particles" are real. There seems to be a
> movement in some European circles that they are not real. For example, I got
> booted off physicsforums.com for arguing that they are real

whoa!  what was your name or handle, Fred?  they didn't boot me off (in
fact, at one time i was a "Science advisor", something i didn't take
very seriously) but one of the mentors was *very* rude to me once and i
asked Greg to remove my account and he would not.  so instead he removed
my SA status at my request.

--

r b-j                  r...@audioimagination.com

"Imagination is more important than knowledge."

Re: Discussion with Prof. Strassler on virtual particles FrediFizzx 7/26/12 11:30 PM
"robert bristow-johnson" <r...@audioimagination.com> wrote in message
news:jut00o$nfs$1@dont-email.me...
> On 7/26/12 11:03 PM, FrediFizzx wrote:
>>
>>
>> I am glad you think that virtual "particles" are real. There seems to be
>> a
>> movement in some European circles that they are not real. For example, I
>> got
>> booted off physicsforums.com for arguing that they are real
>
> whoa!  what was your name or handle, Fred?  they didn't boot me off (in
> fact, at one time i was a "Science advisor", something i didn't take very
> seriously) but one of the mentors was *very* rude to me once and i asked
> Greg to remove my account and he would not.  so instead he removed my SA
> status at my request.

FrediFizzx was my handle same as here.  I had just signed up and less than a
week later I was booted off.  Just as I was putting on the fine touches to
my argument that are impossible to "wiggle" out of.  No big deal as that
forum is kind of lame for anything new and different.

Best,

Fred Diether

Re: Discussion with Prof. Strassler on virtual particles FrediFizzx 7/27/12 11:09 PM
"FrediFizzx" <fredi...@hotmail.com> wrote in message
news:a7eb7nFtmsU1@mid.individual.net...
> Below is a discussion I was having with Prof. Strassler on,
>
> http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/
>
> My discussion starts here if this link works or scroll down near the
> bottom.
>
> http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/#comment-14599
>
> Seems he has turned off replies for the thread (censored me) so I will
> have
> to reply to his last comments here (see near the end).

Correction:  There was no censoring.  It was just due to the screwy way the
blog is setup; I had to reply to myself earlier in the thread to reply to
the thread.

Best,

Fred Diether

Re: Discussion with Prof. Strassler on virtual particles ben6993 7/28/12 6:37 AM
On Friday, 27 July 2012 04:03:41 UTC+1, FrediFizzx  wrote:
> ......
> I am glad you think that virtual "particles" are real. There seems to be a
> movement in some European circles that they are not real. For example, I got
>
> .......
>
> Take muon decay as an example. If there isn't a real virtual W boson
> involved, the muon could never decay. That virtual W boson has all the same
> properties as a "real" W boson except for it is "off mass shell". So your
> "disturbance" here sure smells like a W boson particle. Now, I think that
> with lower energy Coulomb type interactions, the "disturbance" connotation
> could be appropriate. Perhaps you mentioned that above as I did not read all
> of the preceding comments.
>........


In my preon model, the preons have sub-preons rotating at c and have no mass. A particle can move at linear speed c or not depending on the interaction effect between its constituent preons.  When a muon collapses a Higgs field, the following could happen:

muon- +   Higgs       --> neutrino +    W-
o@    +  ooo'o'@@@'@' -->  oo@@'   +   oo'o'@@@'

Then   W-  -->   electron  + antineutrino
oo'o'@@@'  -->     o@      +   o'o'@'@

(Where o is an empty preon, @ is a preon full of contents (sub-preons) and ' denotes an antiparticle.)

The W- here is an intermediate step, and its preons recombine into electron + antineutrino.  The interaction could have been written in one line without the W-.  The six preons of the W- have no individual masses.  The W- mass arises from interaction of the six preon motions.  It doesn't seem surprising that the W- mass in this interaction may not get sufficient time to show up, ie for its preons to interact.  Like guests turning up for a party that have to leave before they get chance to speak to anyone.

Can we have 'virtual' fields too?  Wouldn't it be sod's law if the visible universe was made from an inflated field that was a virtual field before inflation.  From a frozen wave?  Ie maybe not even made from a 'real' field?  

Ben
Not a physicist

Re: Discussion with Prof. Strassler on virtual particles ben6993 7/31/12 11:18 AM
I have realised this morning, thinking about the issue in this thread, ie the decay of a muon to an electron, that my model can explain  neutrino oscillations of electron neutrino <-> muon neutrino <-> taon neutrino.  Moreover, it does not need to use neutrinos which are identical to antineutrinos.  I will post further details in my Implications II thread.

neutrino +   Higgs       -->  neutrino +   neutrino + antineutrino
oo@@'   +  ooo'o'@@@'@'  -->  oo@@'    +     oo@@'  +   o'o'@'@

Then
neutrino +   neutrino + antineutrino -->     Higgs       +   neutrino      
oo@@'    +     oo@@'  +   o'o'@'@    -->  ooo'o'@@@'@'   +   oo@@'

The incoming and outgoing neutrinos are/can be different neutrinos with different energies.  This is very similar to the decay mode of a muon to an electron in the above posts.

It works with an antineutrino also:

antineutrino +   Higgs     -->  antineutrino +   neutrino + antineutrino
o'o'@'@   +  ooo'o'@@@'@'  -->  o'o'@'@      +     oo@@'  +   o'o'@'@

Then
antineutrino +   neutrino + antineutrino -->  Higgs          +   antineutrino      
o'o'@'@      +     oo@@'  +   o'o'@'@    -->  ooo'o'@@@'@'   +   o'o'@'@

That seems to be neutrino flavour oscillations for neutrinos with different strutures than antineutrinos.  No need for them to be Majorana particles.

Ben
Not a physicist