The Vacuum Fluctuation Myth - Comments

  • #151
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The concept of virtual particles is well-defined and useful when restricted to its use in Feynman diagrams and associated technical discussions. But it is highly misleading when used to argue about vacuum fluctuations, as if these were processes happening in space and time.
I agree. Peter's post looked much more general, however, including Feynman diagrams.
 
  • #152
vanhees71
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So would you like to hear my theory on what virtual particles are? I offered to explain this to D. J. Griffiths, as he is a neighbor of mine, but he has mysteriously remained silent. :rolleyes:
Well, Griffiths may be busy with his research and teaching at the university, and from my own experience I can say that if somebody comes by my office, whom I've never seen in my live before, saying he "wants just to discuss about Einstein/relativity, quantum theory, etc." I always pretent to have no clue about these subjects. Then they leave my office quickly. Once, when I was still a diploma student, I was uncareful enough to answer an email of this type. The guy claimed (first indication of a dangerous person) that he had "disproven Einstein", and that he wanted to present his theory to me. I read the rest of the long e-mail, and it was garbage. Then I answered him, explaining what's garbage. That wasn't a good idea, because I got swamped with e-mails of the guy, which at one point I simply ignored. One day, he appeared in person, and it took the whole afternoon to get finally rid of him. Understandably that's why physicists tend to ignore such attempts to disproved established science. So Griffiths's "silence" is everything else than mysterious, it's shear self-defence against unnecessary distruction from work ;-).
 
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  • #153
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Um you quoted someone else that isn't my quote lol
 
  • #154
A. Neumaier
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Not all models in cosmology are semiclassical Loop quantum gravity certainly isn"t
My statement was made in context. Loop quantum gravity makes no assertion about Higgs.
 
  • #155
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Oh and what about field of quantum geometrodynamics? Or the following equation from a LQC article.

[tex] \stackrel{Action}{\overbrace{\mathcal{L}}} \sim \stackrel{relativity}{\overbrace{\mathbb{R}}}- \stackrel{Maxwell}{\overbrace{1/4F_{\mu\nu}F^{\mu\nu}}}+\stackrel{Dirac}{\overbrace{i \overline{\psi}\gamma_\mu\psi}}+\stackrel{Higg's}{\overbrace{\mid D_\mu h\mid-V\mid h\mid}} +\stackrel{Yugawa-coupling}{\overbrace{h\overline{\psi}\psi}} [/tex]

I suppose next your going to claim that The entire findings of a virtual particle cloud in a proton shown by LQCD is wrong too
 
  • #156
PeterDonis
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It is challenging to answer "how does a neutron decay" or "how does the study of rare decays helps with new physics searches" without the concept of virtual particles.
I don't see why it should be. For example, I learned about neutron decay in my nuclear physics classes in college without anyone ever mentioning virtual particles.

the experts you mention later are using the concept of virtual particles exactly in those cases.
As I said, they're experts. My post was directed at non-experts.
 
  • #157
A. Neumaier
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Oh and what about field of quantum geometrodynamics? Or the following equation from a LQC article.

[tex] \stackrel{Action}{\overbrace{\mathcal{L}}} \sim \stackrel{relativity}{\overbrace{\mathbb{R}}}- \stackrel{Maxwell}{\overbrace{1/4F_{\mu\nu}F^{\mu\nu}}}+\stackrel{Dirac}{\overbrace{i \overline{\psi}\gamma_\mu\psi}}+\stackrel{Higg's}{\overbrace{\mid D_\mu h\mid-V\mid h\mid}} +\stackrel{Yugawa-coupling}{\overbrace{h\overline{\psi}\psi}} [/tex]
You chase me through the whole physics literature... But this is the last time I answer. My context was your comment ''There are numerous professional researches ongoing on the aspects of the Higgs field I just mentioned.'' (and the aspects you had mentioned were ''the non zero VeV of the Higg's field'' and ''that due to the non zero VeV we may be in a false vacuum state.'' I see none of these in the formula you just displayed. Note that a ''false vacuum state'' does not belong to the set of physical states of a field theory since it is incompatible with causality. Hence we cannot be in such a state.
 
  • #158
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I'm chasing you through these branches of physics because your inplying they are all wrong. As they do not consider virtual particles as just internal lines on a feyman diagram. That individual virtual particles do not have sufficient momentum to cause action. Collectively in a finite volume they can
 
  • #159
rubi
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I'm chasing you through these branches of physics because your inplying they are all wrong. As they do not consider virtual particles as just internal lines on a feyman diagram. That individual virtual particles do not have sufficient momentum to cause action. Collectively in a finite volume they can
LQG has neither Feynman diagrams nor virtual particles.
 
  • #160
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then how do explain spinfoam action below a quanta of energy? How do you account for any energy/density below a quanta? You certainly cannot state energy exists on its own as energy is a property.

https://arxiv.org/abs/1201.4598

"This means that, although individual terms in the perturbation expansion of a physical amplitude may diverge due to radiative corrections involving closed loops of virtual particles, "

Direct quote from the "Introductory to loop quantum cosmology" article.
 
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  • #161
rubi
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then how do explain spinfoam action below a quanta of energy? How do you account for any energy/density below a quanta? You certainly cannot state energy exists on its own as energy is a property.
None of these questions make sense.

https://arxiv.org/abs/1201.4598

"This means that, although individual terms in the perturbation expansion of a physical amplitude may diverge due to radiative corrections involving closed loops of virtual particles, "
Please don't just type "virtual particle" into the search field of your PDF viewer and randomly quote sentences. If you had read Abhay's article, you would have seen that he is talking about a completely different theory and not about LQG. And he explains that this different theory was not successful. Moreover, even if it was, the Arnold's comments would still apply to it.
 
  • #162
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I'm chasing you through these branches of physics because your inplying they are all wrong.
Well, so almost every textbook on QFT imply "they are all wrong"... Have you taken any course in quantum field theory? Because as far as I can see, only people who haven't have issues with what A. Neumaier wrote in his insights. All those who really learnt QFT during their studies agree with what he wrote. That's weird, isn't it?
 
  • #163
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Oh really then he can answer my concerns on these branches of physics and how more than a few physicists state virtual particles are real and not just internal lines.

Considering he is specifically stating they are wrong to do so. That's not an unreasonable request
 
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  • #164
OmCheeto
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Um you quoted someone else that isn't my quote lol
That was me he was quoting.

Well, Griffiths may be busy with his research and teaching at the university, and from my own experience I can say that if somebody comes by my office, whom I've never seen in my live before, saying he "wants just to discuss about Einstein/relativity, quantum theory, etc." I always pretent to have no clue about these subjects. Then they leave my office quickly. Once, when I was still a diploma student, I was uncareful enough to answer an email of this type. The guy claimed (first indication of a dangerous person) that he had "disproven Einstein", and that he wanted to present his theory to me. I read the rest of the long e-mail, and it was garbage. Then I answered him, explaining what's garbage. That wasn't a good idea, because I got swamped with e-mails of the guy, which at one point I simply ignored. One day, he appeared in person, and it took the whole afternoon to get finally rid of him. Understandably that's why physicists tend to ignore such attempts to disproved established science. So Griffiths's "silence" is everything else than mysterious, it's shear self-defence against unnecessary distruction from work ;-).
I can assure you, that I have no "theories" of my own.
I would describe my thoughts as; "hmmmmmm..... Perhaps these quantum physicists can visualize extra dimensions, which we mere mortals, can not".

Have you ever seen this video?


Things don't make sense, when seen in two dimensions, when they are three dimensional.
I imagine that Quantum Mechanics, being hyper-dimensional, IMHO, is kind of like that.

ps. The ":rolleyes:" at the end of my comment should have clued you in that his actions, were totally understandable. :smile:
 
  • #165
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So Neumaiur are you going to address the issue that although an individual virtual particle doesn't cause action a group of virtual particles can ?
This is precisely what I have been trying to get you to answer.

Is that not what the field perturbations of a S matrix describing?
field/perturbations generically described as virtual particles and field excitations generically a real particle?
 
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  • #166
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You chase me through the whole physics literature... But this is the last time I answer. My context was your comment ''There are numerous professional researches ongoing on the aspects of the Higgs field I just mentioned.'' (and the aspects you had mentioned were ''the non zero VeV of the Higg's field'' and ''that due to the non zero VeV we may be in a false vacuum state.'' I see none of these in the formula you just displayed. Note that a ''false vacuum state'' does not belong to the set of physical states of a field theory since it is incompatible with causality. Hence we cannot be in such a state.
Where are you getting incompatible with causality from? Are you ignoring multiparticle system states? Why can't you have a global distribution of field perturbations?

Which brings us right back to my original post which you called gibberish.

I reiterate there are no particles only fields. Soeaking of my original post you objected to. What do you call the propogator contributions of field perturbations ie how off shell the particle is
https://en.m.wikipedia.org/wiki/Propagator

http://www.google.ca/url?sa=t&source=web&cd=14&ved=0ahUKEwisvJjWzrvRAhXEw1QKHS4xAagQFghOMA0&url=http://www-pnp.physics.ox.ac.uk/~barra/teaching/feynman.pdf&usg=AFQjCNFXFEf7xQrDFKy1hG1mb6SlMwmSKg&sig2=3Ia1ETeyUQaCxwSZR3GFUA

is the propogator not a plane wave? Yet you stated their is no wavefunction for virtual particles in your reply to my original post.
 
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  • #167
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A. Neumaier submitted a new PF Insights post
Hi Arnold, I really want to thank you for this article, as I find the topic of the Vacuum (or spacetime) to be truly interesting.

It was physicist Andrei Sakharov who said "the mysteries of the vacuum will be the great challenge for 21st-century physics"

But after having read you tell me what I shouldn't believe, I then really want to know what I should believe.
You've just told me why it's wrong to believe that 6 x 7 = 45 and I hear you on that. But now I want to know what the actual answer is.

And as far as I can see, you're not explicitly saying "the answer isn't 45" - you're instead saying "we as yet have no reason to believe it's 45"

So I'm looking for someone to tell me what the Vacuum is actually made out of, if it's not made out of "virtual particles".
 
  • #168
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removing all matter a scalar field would be my answer
 
  • #169
A. Neumaier
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what the Vacuum is actually made out of, if it's not made out of "virtual particles".
It is made of nothing, it is just a container for real stuff. You could as well ask what the interior of an empty bottle contains.
 
  • #170
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removing all matter a scalar field would be my answer
Okay, but what is causing/producing the scalar field? There seem to be fluctuations happening in the Vacuum - Black Body radiation indicates this. DeBroglie wavelength of objects also seems to indicate this. So what is that stuff? What is causing these fluctuations/disturbances in the Scalar Field?
 
  • #171
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It is made of nothing, it is just a container for real stuff. You could as well ask what the interior of an empty bottle contains.
But conceptually, a bottle doesn't need to have black body radiation - the fact that it does says there is something more than the bottle which is there.
Conceptually, a bottle doesn't need to have a Casimir force inside it - the fact that it does says there is something more than bottle which is there.

I feel as if you've just told me to ignore that photons have wave characteristics - ie. "just ignore it, this is a mere artifact of observation, and doesn't signify anything"

I cannot ignore it, I cannot pretend it isn't there - I want to know what's causing it. I want to know if whatever's causing it has its own deeper properties, which perhaps I can't immediately/easily see.
 
  • #172
A. Neumaier
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Okay, but what is causing/producing the scalar field?
The fields are there, all the time. The vacuum state is just the special state of the system where the state is Poincare invariant - timeless, spaceless, due to the symmetry. This is like an empty, infinitely extended container - an abstraction.

Real spacetime is nowhere a vacuum. it is filled everywhere with fields - gravity, radiation, and traces of matter - with big lumps here and there. These fields are not in a pure vacuum state, however, not even locally, far away from stars and planets.

If you ask for a cause of that, you need to ask God. The answer is outside the realm of physics.
 
  • #173
A. Neumaier
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a bottle doesn't need to have black body radiation - the fact that it does says there is something more than the bottle which is there.
It says that the bottle has an exterior which is not empty, from which the radiation comes. This means that a real bottle is not really empty. The bottle I was talking about was an abstraction, just like the vacuum of quantum field theory.

So, the effects in an apparent piece of vacuum (apparent since there are invisible fields in any vacuum that can be created experimentally) between pieces of matter are caused by the matter and fields surrounding the vacuum,.
 
  • #174
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The fields are there, all the time. The vacuum state is just the special state of the system where the state is Poincare invariant - timeless, spaceless, due to the symmetry. This is like an empty, infinitely extended container - an abstraction.

Real spacetime is nowhere a vacuum. it is filled everywhere with fields - gravity, radiation, and traces of matter - with big lumps here and there. These fields are not in a pure vacuum state, however, not even locally, far away from stars and planets.

If you ask for a cause of that, you need to ask God. The answer is outside the realm of physics.

Sir, I don't wish to invoke a metaphysical explanation, I feel that physics and the scientific method can probe everything usefully.

Blackbody radiation can be measured reliably, and isn't overly dependent on whatever combination of cosmic events (radiating suns, exploding stars, black holes) may be happening around the rest of the cosmos at the time.
Casimir force can be measured reliably, and experimental observation of it doesn't give radically different results when done with appropriate experimental rigor.

Furthermore, the very ideas of waves or particles or fields are themselves concepts we apply onto reality. If I choose to call an automobile a particle, then that's my choice, and as long as I maintain a logical consistency, then I can describe the universe that way.

Saying that it's wrong to choose to describe Vacuum fluctuations with particles, is like saying it's wrong to describe light using photon particles.
If the fluctuations of the Scalar Field exist, then there's no reason why the idea of particles can't be adopted to describe it.
 
  • #175
A. Neumaier
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Blackbody radiation can be measured reliably
Black body radiation is caused by the electromagnetic field. Hawking radiation is real particles created by the gravitational field. Nothing is created by either the vacuum or by virtual particles.
That's the scientific part.

But you wanted a cause for the field itself, which is metaphysics.
 
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