De Broglie-Bohm theory and Bohm-like models - how is vacuum treated?

In summary: Quoting: "Hence, according the Bohmian mechanics the particles are not moving but on the other hand they possesses average kinetic energy according to quantum mechanics. The reason is that Q is not potential but kinetic energy stored as the Fisher entropy."So some (real) particles in the vacuum are moving??Can anyone shed light on why this statistical approach is flawed?@A. Neumaier you are cited in the above publication ... but the paper does not describe the vacuum they are talking about, except that it fluctuates. I'm at a loss.No. In this theory particles of the Standard Model (and gravitons of effective quantum gravity) do not have trajectories at all, not
  • #1
asimov42
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4
Hi all,

I've been looking at de Broglie-Bohm theory and more recent attempts at Bohm-like models that are relativistic and attempt to reproduce QFT. What I'm not clear on (non-expert) is how the vacuum is modeled in these cases? If we have a set of infinite quantum harmonic oscillators, wouldn't Bohm-like models have implications that there exist an infinite number of oscillators with exact positions at each point? (not getting into renormalization)

In particular, this paper https://arxiv.org/pdf/0903.0283.pdf (which has been published in New Adv. Phys. 3 (2009) 35-44) seems to suggest that (real Bohmian) particles are pushed around by vacuum fluctuations (@A. Neumaier may have something to say). The paper implies a statistical mechanics-type solution, ... but if this were true, wouldn't it be the case that you could extract energy from the vacuum?

Sorry if the above is not very clear - I'm having a hard time with the interpretation (of the interpretation...).
 
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  • #2
asimov42 said:
seems to suggest that (real Bohmian) particles are pushed around by vacuum fluctuations (@A. Neumaier may have something to say).
I have nothing positive to say about Bohmian mechanics.
 
  • #3
Indeed there seem to be some fairly big issues - but perhaps it cannot be dismissed outright? This review (http://philsci-archive.pitt.edu/3026/1/bohm.pdf) does mention the vacuum in Bohmian-like theories, but I'm still not sure I'm any closer to understanding what is actually meant ...
 
  • #4
It means nothing. According to @Demystifier (aka Hrvoje Nikolic), the Bohmian vacuum is full of an infinite number of Bohmian particles with zero effectivity. None of them is virtual, though.
 
  • #5
A. Neumaier said:
It means nothing. According to @Demystifier (aka Hrvoje Nikolic), the Bohmian vacuum is full of an infinite number of Bohmian particles with zero effectivity. None of them is virtual, though.
It was my first paper on Bohmian mechanics. In the meantime I developed different (better) approaches to treat QFT with Bohmian mechanics.
 
  • #6
Demystifier said:
It was my first paper on Bohmian mechanics. In the meantime I developed different (better) approaches to treat QFT with Bohmian mechanics.
Thus there are more inequivalent Bohmian QFTs than there are authors on the subject?
 
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  • #7
asimov42 said:
If we have a set of infinite quantum harmonic oscillators, wouldn't Bohm-like models have implications that there exist an infinite number of oscillators with exact positions at each point?
As I said above, there are more than one approaches to Bohmian QFT. In the approach proposed in my signature above (which now I think is the most promising approach) , continuum field theory is just an approximation for a theory that is really discrete. This means that in the vacuum you really have a large but finite number of point-particles, each with a definite (you would say "exact") position.
 
  • #8
A. Neumaier said:
Thus there are more inequivalent Bohmian QFTs than there are authors on the subject?
Yes. :smile:
 
  • #9
Demystifier said:
As I said above, there are more than one approaches to Bohmian QFT. In the approach proposed in my signature above (which now I think is the most promising approach) , continuum field theory is just an approximation for a theory that is really discrete. This means that in the vacuum you really have a large but finite number of point-particles, each with a definite (you would say "exact") position.
Thus the vacuum is still very full, with probably much more than ##10^{79}## particles. Do the photons and gravitons in your vacuum have positions, too?
 
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  • #10
A. Neumaier said:
Thus the vacuum is still very full, with probably much more than ##10^79## particles. Do the photons and gravitons in your vacuum have positions, too?
No. In this theory particles of the Standard Model (and gravitons of effective quantum gravity) do not have trajectories at all, not even in non-vacuum states.
 
  • #11
the paper I noted above, https://arxiv.org/pdf/0903.0283.pdf, has the behaviour of a harmonic oscillator in the ground state as being an 'ensemble' of 'realizations' where the there is motion... only on average is its motion zero.

I don't understand how this proposal can possibly jive with what we think of as the vacuum ...

Quoting: "Hence, according the Bohmian mechanics the particles are not moving but on the other hand they possesses average kinetic energy according to quantum mechanics. The reason is that Q is not potential but kinetic energy stored as the Fisher entropy."

So some (real) particles in the vacuum are moving??
 
  • #12
Can anyone shed light on why this statistical approach is flawed?

@A. Neumaier you are cited in the above publication ... but the paper does not describe the vacuum they are talking about, except that it fluctuates. I'm at a loss.
 
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  • #13
Demystifier said:
No. In this theory particles of the Standard Model (and gravitons of effective quantum gravity) do not have trajectories at all, not even in non-vacuum states.
But then Bohm's mechanics is no longer an approximation of your pseudo Bohmian QFT! Or how would you get it when considering a tiny part of your universe and doing there a scattering experiment?
 
  • #14
asimov42 said:
Can anyone shed light on why this statistical approach is flawed?

@A. Neumaier you are cited in the above publication ... but the paper does not describe the vacuum they are talking about, except that it fluctuates. I'm at a loss.
Why are you interested?
 
  • #15
A. Neumaier said:
But then Bohm's mechanics is no longer an approximation of your pseudo Bohmian QFT!
Do you see it as a problem?

I would compare it with evolution of string theory. String theory was originally envisioned as a theory of nuclear force, but later it turned out that it is much better interpreted as a theory of something more fundamental. Similarly, Bohmian mechanics was originally envisioned as a theory of electrons and other Standard Model particles, but now I propose that it is better interpreted as a theory of something more fundamental.
 
  • #16
asimov42 said:
Hi all,

I've been looking at de Broglie-Bohm theory and more recent attempts at Bohm-like models that are relativistic and attempt to reproduce QFT. What I'm not clear on (non-expert) is how the vacuum is modeled in these cases? If we have a set of infinite quantum harmonic oscillators, wouldn't Bohm-like models have implications that there exist an infinite number of oscillators with exact positions at each point? (not getting into renormalization)

In particular, this paper https://arxiv.org/pdf/0903.0283.pdf (which has been published in New Adv. Phys. 3 (2009) 35-44) seems to suggest that (real Bohmian) particles are pushed around by vacuum fluctuations (@A. Neumaier may have something to say). The paper implies a statistical mechanics-type solution, ... but if this were true, wouldn't it be the case that you could extract energy from the vacuum?

Sorry if the above is not very clear - I'm having a hard time with the interpretation (of the interpretation...).

@Demystifier and @A. Neumaier , This paper says that particles are pushed around by vacuum fluctuations and this is the reason for their random behavior. But are vacuum fluctuations this strong to apply a meaningful force to particles such that their trajectory is altered?
 
  • #17
asimov42 said:
seems to suggest that (real Bohmian) particles are pushed around by vacuum fluctuations
Ali Lavasani said:
This paper says that particles are pushed around by vacuum fluctuations and this is the reason for their random behavior. But are vacuum fluctuations this strong to apply a meaningful force to particles such that their trajectory is altered?
Vacuum fluctuations are not events happening in space and time. See my Insight articles on this subject.
 
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  • #18
A. Neumaier said:
Vacuum fluctuations are not events happening in space and time. See my Insight articles on this subject.
So you suggest the idea of the paper is totally wrong?
 
  • #19
Ali Lavasani said:
So you suggest the idea of the paper is totally wrong?
totally misleading.
 
  • #20
A. Neumaier said:
totally misleading.
Thanks. As far as I understand, you believe in orthodox nonrealistic models, in which of course there is nothing fluctuating in real time, it's all about the inherent uncertainty in the number of particles. However, I think Bohmians and other realistics need to invoke such real time particle creation and annihilation processes if they want to have the same predictions as the orthodox QFT.
 
  • #21
Ali Lavasani said:
Thanks. As far as I understand, you believe in orthodox nonrealistic models, in which of course there is nothing fluctuating in real time, it's all about the inherent uncertainty in the number of particles.
No, @A. Neumaier is a realist. But he is not satisfied with the "official" realist interpretations, so he proposed his own realist interpretation called thermal interpretation.

Ali Lavasani said:
However, I think Bohmians and other realistics need to invoke such real time particle creation and annihilation processes if they want to have the same predictions as the orthodox QFT.
No they don't. Virtual particles are non-real even in realistic interpretations such as Bohmian mechanics.
 
  • #22
Demystifier said:
No, @A. Neumaier is a realist.No they don't. Virtual particles are non-real even in realistic interpretations such as Bohmian mechanics.
If they are non-real, how can they have an effect on other particles, apply a noticable force on them, and push them around (in the article cited on this thread)?
 
  • #23
Ali Lavasani said:
If they are non-real, how can they have an effect on other particles, apply a noticable force on them, and push them around (in the article cited on this thread)?
I like to compare it with negative money. If negative money (called debth on a bank account) is not real, then how can it affect ones life (the ability to buy things)? The answer is that it is just a mathematical trick used to compute the effect of something real.
 
  • #24
Demystifier said:
I like to compare it with negative money. If negative money (called debth on a bank account) is not real, then how can it affect ones life (the ability to buy things)? The answer is that it is just a mathematical trick used to compute the effect of something real.
Thanks! Actually I had seen papers on BM QFT suggesting that particles actually pop in and out of existence. See this one for instance: https://arxiv.org/abs/quant-ph/0701085

Also, what is exactly responsible for the force applied on particles and pushing them around, which is kinda being described by virtual electron-positron pairs? I posted a question regarding the lamb shift here: https://www.physicsforums.com/threads/how-and-in-what-atoms-does-the-lamb-shift-occur.970493/

And, the question is, are these vacuum fluctuations really that strong to be able to modify the electric potential, affect electrons' trajectories and push them around? I had heard that they are only noticeable within a Compton wavelength of the particle producing the electric field.
 
  • #26
Demystifier said:
Where does this paper suggest that?
Maybe this one (Fig.1) is more clear: https://arxiv.org/pdf/quant-ph/0303156.pdf. The particles are having "world lines" in the spacetime, after which they kinda disappear.
 
  • #27
Ali Lavasani said:
Maybe this one (Fig.1) is more clear: https://arxiv.org/pdf/quant-ph/0303156.pdf. The particles are having "world lines" in the spacetime, after which they kinda disappear.
Yes, but those particle correspond to real particles, not to the virtual ones.
 
  • #28
So what are these real particles that appear and disappear? Are they electron-positron pairs being created and annihilated, namely "vacuum fluctuations"?
 
  • #29
Ali Lavasani said:
So what are these real particles that appear and disappear? Are they electron-positron pairs being created and annihilated, namely "vacuum fluctuations"?
They are the first but not the second. Vacuum fluctuations have nothing to do with electron-positron pairs being created and annihilated; see the articles cited in post #17.
 

1. What is the De Broglie-Bohm theory?

The De Broglie-Bohm theory, also known as the pilot-wave theory, is a quantum mechanics interpretation that suggests particles have both a physical position and a "pilot wave" that guides their movement. This theory was first proposed by Louis de Broglie and expanded upon by David Bohm in the 1950s.

2. How does the De Broglie-Bohm theory differ from other interpretations of quantum mechanics?

The De Broglie-Bohm theory differs from other interpretations, such as the Copenhagen interpretation, in that it does not rely on the concept of wavefunction collapse. Instead, particles have definite positions and their movements are determined by the pilot wave, which evolves according to the Schrödinger equation.

3. What are Bohm-like models?

Bohm-like models are variations of the De Broglie-Bohm theory that aim to address some of its limitations. These models still rely on the concept of a pilot wave, but they may introduce modifications to the original theory, such as non-local effects or additional hidden variables.

4. How is the vacuum treated in De Broglie-Bohm theory and Bohm-like models?

In these theories, the vacuum is treated as a state of the universe in which there are no particles present. However, the pilot wave still exists and can potentially interact with virtual particles, which are constantly popping in and out of existence in the vacuum according to quantum field theory.

5. What are the implications of De Broglie-Bohm theory and Bohm-like models for our understanding of quantum mechanics?

These theories provide a different perspective on the nature of particles and their behavior at the quantum level. They also suggest that there may be underlying deterministic laws governing the universe, rather than the probabilistic nature of traditional quantum mechanics. However, these theories are still controversial and have not been widely accepted by the scientific community.

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