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Do virtual particles exist?


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Posted (edited)

Are virtual particle pockets of energy? In other words: are virtual particles force carriers? 

If not, if they’re in no way a form of energy, and in no way associated with kinetic energy because they’re not actually moving/vibrating at all, but rather just ‘theoretical and mathematical constructs’, as some argue, then why are they called ‘particles’ in the first place? How is that not a misleading term, because, if you’re a particle somewhere in the universe, you’re definitely not ‘nothing’ (which is what ‘a mathematical construct’ basically implies). And if you’re not nothing, that means you therefore must be something, i.e. some sort of kinetic/potential energy, albeit very little. A little bit is still something.

Three other things don’t make sense to mee if virtual particles don’t exist, and are to be regarded as mere mathematical constructs:

1. If the mathematics describes something that is not out there in the real world, if for instance those virtual photons that appear in Feynman diagrams don't describe what's taking place in reality, then why do we take the those mathematical descriptions seriously?

2. Why hasn’t some of the quantum fluctuations hypotheses, that describe how the universe came into existence, been refuted immediately? For instance the ‘vacuum genesis’ (or: ‘zero-energy universe hypothesis’) has been proposed by Edward P. Tryon. He suggested that the Universe may be a large-scale quantum-mechanical vacuum fluctuation (since vacuum fluctuations appear as virtual particles, which are always created in particle-antiparticle pairs). I don’t intend in invoke a discussion about the plausibility of this hypothesis, I’m only bringing it up to find out why it hasn’t been refuted immediately because, if virtual particles don’t describe reality, this hypothesis should never have been regarded as a potential candidate in the first place, but only as a mathematical theory, without the reference to the universe we're living in. 

3. Virtual particles are also described in the phenomenon of ‘Hawking radiation’, in which a virtual pair that appears very close to the event horizon, one may ‘steal’ energy from the other and escape as a real particle, while the other is drawn back in and disappears, effectively stealing the energy from the black hole. Virtual particles, once again, seems to be not simply a mathematical construct, but actually out there, interacting, located close to black holes (which are also actually out there of course, nobody would deny the existence of black holes). So virtual-ness seems to be able to embody a role between ‘not real’ and ‘real’, which would mean that they are forces of nature that do exist, albeit in some kind of purgatory-like state, limited by Heisenberg's uncertainty principle.

So, do virtual particles exist? 
Please prelude your answer by first a 'yes' or a 'no'.

Edited by MarkE
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No.

And yes. They are very contingent concepts. As... perhaps most other concepts?

"Exist" is not a good verb for describing reality, in the last analysis:

Does the upper part of an electron exist? Does that look in my sweetheart's eyes exist? Does a name that hasn't been pronounced exist?

Virtual particles are effectual, I would say. They don't exist, but they appear in calculations. If you measure their presence, then they "exist", but they no longer are virtual. That's the kind of circle we're in. And I don't know whether that's a satisfactory explanation, but that like the best I can do.

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23 minutes ago, MarkE said:

Are virtual particle pockets of energy? In other words: are virtual particles force carriers? 

If not, if they’re in no way a form of energy, and in no way associated with kinetic energy because they’re not actually moving/vibrating at all, but rather just ‘theoretical and mathematical constructs’, as some argue, then why are they called ‘particles’ in the first place? How is that not a misleading term, because, if you’re a particle somewhere in the universe, you’re definitely not ‘nothing’ (which is what ‘a mathematical construct’ basically implies). And if you’re not nothing, that means you therefore must be something, i.e. some sort of kinetic/potential energy, albeit very little. A little bit is still something.

Three other things don’t make sense to mee if virtual particles don’t exist, and are to be regarded as mere mathematical constructs:

1. If the mathematics describes something that is not out there in the real world, if for instance those virtual photons that appear in Feynman diagrams don't describe what's taking place in reality, then why do we take the those mathematical descriptions seriously?

2. Why hasn’t some of the quantum fluctuations hypotheses, that describe how the universe came into existence, been refuted immediately? For instance the ‘vacuum genesis’ (or: ‘zero-energy universe hypothesis’) has been proposed by Edward P. Tryon. He suggested that the Universe may be a large-scale quantum-mechanical vacuum fluctuation (since vacuum fluctuations appear as virtual particles, which are always created in particle-antiparticle pairs). I don’t intend in invoke a discussion about the plausibility of this hypothesis, I’m only bringing it up to find out why it hasn’t been refuted immediately because, if virtual particles don’t describe reality, this hypothesis should never have been regarded as a potential candidate in the first place, but only as a mathematical theory, without the reference to the universe we're living in. 

3. Virtual particles are also described in the phenomenon of ‘Hawking radiation’, in which a virtual pair that appears very close to the event horizon, one may ‘steal’ energy from the other and escape as a real particle, while the other is drawn back in and disappears, effectively stealing the energy from the black hole. Virtual particles, once again, seems to be not simply a mathematical construct, but actually out there, interacting, located close to black holes (which are also actually out there of course, nobody would deny the existence of black holes). So virtual-ness seems to be able to embody a role between ‘not real’ and ‘real’, which would mean that they are forces of nature that do exist, albeit in some kind of purgatory-like state, limited by Heisenberg's uncertainty principle.

So, do virtual particles exist? 
Please prelude your answer by first a 'yes' or a 'no'.

I'm going to start by saying I'm a mere chemist who learnt some quantum chemistry 40 years ago, so I am not an authority. However I have read a bit about this, as I found it confusing. What follows is my understanding.

I'm also going to ignore the instruction to start with yes or no, as I think you pose a bit of a false antithesis. Sorry. 

I have to take issue with your assumption that to be force carriers these entities need to be "pockets of energy". I think that is wrong at at least two levels. First, energy is not stuff: you can't have a jug of energy. Energy is a property of a system of some kind. Things "have" energy. They can't "be" energy.   Second, I think it is wrong to imagine that virtual particles need to have energy in order to be force carriers. An entity does not have to experience energy gain or loss to experience a force. 

As to whether virtual particles are "real", I'm going to risk annoying you by saying I think it depends what you mean by "real". What seems to be the case is that virtual particles are not particles. They are - so I gather - disturbances in various fields that can be modelled using some of the same mathematics as particles. But the disturbances in the field are "real", in that there are observable consequences of them. 

A year or two ago I came across a very good article about virtual particles by Matt Strassler, here, which may help you. It helped me, anyway:  

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

 

 

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Virtual particles are parts of a mathematical model which describes/predicts quite a few observations and measurements.
Without virtual particles the model would fail.

Does that make them 'real' ?

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7 hours ago, MarkE said:

So, do virtual particles exist? 
Please prelude your answer by first a 'yes' or a 'no'.

Wiki gives in my opinion a pretty good explanation.....

https://en.wikipedia.org/wiki/Virtual_particle

In physics, a virtual particle is a transient quantum fluctuation that exhibits some of the characteristics of an ordinary particle, while having its existence limited by the uncertainty principle. The concept of virtual particles arises in perturbation theory of quantum field theory where interactions between ordinary particles are described in terms of exchanges of virtual particles. A process involving virtual particles can be described by a schematic representation known as a Feynman diagram, in which virtual particles are represented by internal lines.

Virtual particles do not necessarily carry the same mass as the corresponding real particle, although they always conserve energy and momentum. The closer its characteristics come to those of ordinary particles, the longer the virtual particle exists. They are important in the physics of many processes, including particle scattering and Casimir forces. In quantum field theory, forces—such as the electromagnetic repulsion or attraction between two charges—can be thought of as due to the exchange of virtual photons between the charges. Virtual photons are the exchange particle for the electromagnetic interaction.

The term is somewhat loose and vaguely defined, in that it refers to the view that the world is made up of "real particles". It is not. "Real particles" are better understood to be excitations of the underlying quantum fields. Virtual particles are also excitations of the underlying fields, but are "temporary" in the sense that they appear in calculations of interactions, but never as asymptotic states or indices to the scattering matrix. The accuracy and use of virtual particles in calculations is firmly established, but as they cannot be detected in experiments, deciding how to precisely describe them is a topic of debate.

more at link........

 

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7 hours ago, MarkE said:

if you’re a particle somewhere in the universe, you’re definitely not ‘nothing’ (which is what ‘a mathematical construct’ basically implies).

This is the tail wagging the dog. The dictionary does not define physics.

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7 hours ago, MarkE said:

So, do virtual particles exist? 
Please prelude your answer by first a 'yes' or a 'no'.

How can I until you explain exactly what you mean by 'virtual' in Philosophy  ?

There are many effects in Science that are conveniently handled by prefixing the word virtual, although its meaning may vary from application to application.

and that is without properly discussing the meaning of particle and exist.

Does the place described by 'What Three Words' exit for the three words virtual, particles and exist ?

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On 5/6/2021 at 2:37 PM, MarkE said:

So, do virtual particles exist? 
Please prelude your answer by first a 'yes' or a 'no'.

 

Has everybody (MarkE in particular) given up on this one  ?

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1 hour ago, studiot said:

Has everybody (MarkE in particular) given up on this one  ?

My following comments are not intended as cynicism, trolling, fatuousness, or any other negative descriptor, I ask a basic question to which I would be interested in learning some of the possible answers.

Does it matter? Not, whether or not everyone's given up on this thread, but does it matter whether virtual particles are real or not? Virtual particles 'perform' at scales of time and space, and in a medium, that is utterly beyond the experience and mental acuity of a bunch of hyped-up African Apes to understand without the application of a pile of complex metaphors (disguised as mathematics). In my first year of science at secondary school one of the teachers misquoted someone (and I misremembered the misquote) as defining an atom as  "a hole, in a hole, round a hole, on a hole". I have been more than comfortable with that definition ever since. I accept the decriptions of atoms and particles and fields and forces as being convenient labels to help us take a stab at describing "what's going on". But the map is not the territory and an art critic's review of a Picasso is most certainly not the Picasso. Do I have it wrong?

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1 hour ago, Area54 said:

My following comments are not intended as cynicism, trolling, fatuousness, or any other negative descriptor, I ask a basic question to which I would be interested in learning some of the possible answers.

Does it matter? Not, whether or not everyone's given up on this thread, but does it matter whether virtual particles are real or not? Virtual particles 'perform' at scales of time and space, and in a medium, that is utterly beyond the experience and mental acuity of a bunch of hyped-up African Apes to understand without the application of a pile of complex metaphors (disguised as mathematics). In my first year of science at secondary school one of the teachers misquoted someone (and I misremembered the misquote) as defining an atom as  "a hole, in a hole, round a hole, on a hole". I have been more than comfortable with that definition ever since. I accept the decriptions of atoms and particles and fields and forces as being convenient labels to help us take a stab at describing "what's going on". But the map is not the territory and an art critic's review of a Picasso is most certainly not the Picasso. Do I have it wrong?

I think that has to be right.  

In science we make models of the "real" physical world, to predict what we should expect to observe. There comes a point, certainly in QM as I remember it, at which the mathematics is the model.

Is it real? The honest answer has to be that we don't know. All our models are subject to change and further refinement, so we can never say they are 100% real, but only approximations to reality.    

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1 hour ago, Area54 said:

Does it matter?

Only if you think it does...

Virtually, just, describes an attempt to make sense of something we don't understand... 😉 

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6 minutes ago, dimreepr said:

 

Virtually, just, describes an attempt to make sense of something we don't understand... 😉 

What is meant by virtual (virtually is an adverb which refers to verbs, not nouns) is my point.

Yes we do understand virtual and have been using it for centuries.

 

27 minutes ago, exchemist said:

so we can never say they are 100% real

Does you eye see the virual image obtained through a magnifying glass ?

What is the difference between a real and virtual image ?

 

If you understand the difference between pressure and force you are using a good example of another virtual phenomenon.

Consider a gas.

Imagine a frame somewhere in that gas defining an area.

What is the pressure across that frame and is a force acting ?

The frame and its area are virtual as pressure is only exerted on the boundaries of the gas.

In other words it is only realised by the interaction with the real world around it, just like the quantum virtual particle.

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2 hours ago, Area54 said:

But the map is not the territory and an art critic's review of a Picasso is most certainly not the Picasso. Do I have it wrong?

I would tend to develop the argument along these lines. When someone puts forward a theory, there is an honest attempt to explain what we see or measure (let's call that "real"). But then it never stops at that; there are all sorts of concepts that are logically necessary to make the theory consistent.

Taking up on your analogy with the map and the territory; we could ask: Are Meridians and Parallels real? I don't think anybody would say they are. They're just part of the theoretical scaffolding. There are no lines there, really.

In the case of (perturbative) quantum field theory, if you want to describe a particle going from A to B, you always need to include these corrections due to particle-antiparticle pairs (fermions) being produced and re-absorbed before the particle reaches B; or standalone bosons being emitted and re-absorbed. They may just be a consequence of the way in which we partition the world with our theory. If some day people find a non-perturbative formulation of QFT that's entirely consistent and general enough, it may be the case that we can get rid of the concept of virtual particles entirely, and then we see them as just a contingency of the model of perturbative quantum field theory.

The whole rationale of perturbative QFT is that I write down a dynamics that I can solve exactly, and then add smaller and smaller corrections based on calculational convenience. Why should Nature care about what we find easier or more difficult to compute? So maybe virtual particles are a consequence of our theoretical mapping, if I have understood you correctly.

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Posted (edited)

Thanks everyone for taking the time to respond to my question.

In the meantime I asked the same question at some place else, and found my answer. The miscommunication lies within the distinction between Feynman diagrams on the one hand (since these diagrams are not gauge invariant), and the experiments that had been undertaken on the other hand. In the first case, it’s a clear no, but in the second case, experimental evidence (such as the Casimir effect) demonstrate that it’s a yes (which is closest to what @joigus said: yes and no).

This distinction was the answer I was looking for, but thanks anyway everybody for your time to write a reply!

Edited by MarkE
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1 hour ago, MarkE said:

Thanks everyone for taking the time to respond to my question.

In the meantime I asked the same question at some place else, and found my answer. The miscommunication lies within the distinction between Feynman diagrams on the one hand (since these diagrams are not gauge invariant), and the experiments that had been undertaken on the other hand. In the first case, it’s a clear no, but in the second case, experimental evidence (such as the Casimir effect) demonstrate that it’s a yes (which is closest to what @joigus said: yes and no).

This distinction was the answer I was looking for, but thanks anyway everybody for your time to write a reply!

I think the problem here is the definition of "exist" which was not provided.

The explanation of the Casimir effect that invokes virtual particles uses Feynman diagrams

In both of these cases, the answer is clearer if the question were "do virtual particles have a measurable effect" because in both cases, they obviously do, and for physics, that's enough. 

 

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Posted (edited)
46 minutes ago, swansont said:

I think the problem here is the definition of "exist" which was not provided.

The explanation of the Casimir effect that invokes virtual particles uses Feynman diagrams

In both of these cases, the answer is clearer if the question were "do virtual particles have a measurable effect" because in both cases, they obviously do, and for physics, that's enough. 

 

Don't they only have a measurable effect when they combine briefly but individually they are sub-quantum?

Edited by StringJunky
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29 minutes ago, StringJunky said:

Don't they only have a measurable effect when they combine briefly but individually they are sub-quantum?

It's a continual process, and some of the effects have many layers of Feynman diagrams, with multiple loop structures even at the first layers (they tend to get much more complex as you go to more loops), so I don't think you can narrow it down to just the recombination. The whole process is responsible for the contribution, AFAIK. The application of conservation laws at the nodes is bookkeeping.

Plus, I don't know that there would be any way to test this hypothesis 

 

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11 hours ago, swansont said:

It's a continual process, and some of the effects have many layers of Feynman diagrams, with multiple loop structures even at the first layers (they tend to get much more complex as you go to more loops), so I don't think you can narrow it down to just the recombination. The whole process is responsible for the contribution, AFAIK. The application of conservation laws at the nodes is bookkeeping.

Plus, I don't know that there would be any way to test this hypothesis 

 

Thanks.

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