Real or Virtual Particles: Chicken or the Egg?

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Do real particles "cause" virtual particles, or do virtual particles "cause" real particles?

Put another way, is it so that real particles actually exist in and of themselves and interact as normally described by transferring virtual particles with each other.

OR,

Are only virtual particles "real" in the sense of having any sort of actual existence however brief, and it is real particles that are actually just the inference of there being something there in space due to their observed interactions with other real particles also inferred to be there due their mass, charge, etc all mediated by virtual particles.

Are real particles mere consistent patterns of incidental order emergent within the chaos of brief spontaneously created random virtual particles making up the quantum foam of space?

Does this have anything to do with Symmetry Breaking and Lie groups and the relative (localized?) Lagrangian/Hamiltonian balance of KE and PE?
 
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Interpretation dependent
 
sujiwun said:
Do real particles "cause" virtual particles, or do virtual particles "cause" real particles?

What does 'cause' mean?
 
I'd call it an open question. We still don't know exactly what causes mass. There is evidence that all mass might be effective mass due to interaction fields between particles. At least, more and more of the rest mass of particles is shown to be such. If other fundamental charges, namely electric charge and color charge, prove to be similar, we'd be in a situation where one cannot exist without the other.
 
Virtual particles are not real. If people didn't use perturbation theory there would be no discussion about virtual particles, they are not a feature of the real theory. They do not appear in a nonperturbative description.
 
Phrak said:
What does 'cause' mean?

"The law of causality, I believe, like much that passes muster among philosophers, is a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm."

Bertrand Russell
 
DarMM said:
Virtual particles are not real. If people didn't use perturbation theory there would be no discussion about virtual particles, they are not a feature of the real theory. They do not appear in a nonperturbative description.

Are the electrons and quarks, that all matter is made of - being point particles, by definition having no spatial extension - any more real?
 
  • #10
DarMM said:
Virtual particles are not real. If people didn't use perturbation theory there would be no discussion about virtual particles, they are not a feature of the real theory. They do not appear in a nonperturbative description.

It is interpretation dependent

In SM, for example, both "real" and "virtual" particles are "just math" to describe the correlation between macroscopic events

All other definitions of "virtual" particles are sooooo Copenhagen - any definition uses words "measured", "observed", "has enough energy" (=observable), or "incoming and outgoing particles" (outgoing=detected).

I've never seen any definition of virtual particles which can be used in modern non-collapse (decoherence) theories.
 
  • #11
K^2 said:
I'd call it an open question. We still don't know exactly what causes mass. There is evidence that all mass might be effective mass due to interaction fields between particles. At least, more and more of the rest mass of particles is shown to be such. If other fundamental charges, namely electric charge and color charge, prove to be similar, we'd be in a situation where one cannot exist without the other.

How about this for a possible stochastic explanation.

The flux of quantum foam is random, so its net lagrangian should be zero.

Perhaps mass is the result of brief incidental localized emergent non-zero lagrangian - virtual particles...

where the Lagrangian, L = T-V
T = KE = change within the foam
V = PE = constancy within the foam
 
  • #12
Both point particles and fields (either classical or quantum) are not real. They're only models of our reality. Nothing but elements of a mathematical modelation of an experimentally observable reality.
 
  • #13
  • #14
Dmitry67 said:
It is interpretation dependent...
I think a discussion on what is or isn't "really real", will be pointless. Instead I will discuss what the theory itself says. All quantum field theories do not predict the existence of virtual particles. Virtual particles only appear as lines in Feynman diagrams which are attached to the perturbative formulation. What the the theory itself says are real, observable, e.t.c. are the eigenstates of the Hamiltonian, the states which label in and out going asymptotes. The theory predicts the existence of these, it does not predict the existence of virtual particles.

Whether or not the theories predictions are themselves "real" is a separate discussion, but let's not tangle it up with the observation that virtual particles are perturbative artefacts.
 
  • #15
sujiwun said:
Are the electrons and quarks, that all matter is made of - being point particles, by definition having no spatial extension - any more real?
I have never seen where QFT predicts that electrons and quarks are "point particles". QFT has local field interactions "at a point", but the particles themselves always have wavefunctions with finite spatial support.
 
  • #17
DarMM said:
I have never seen where QFT predicts that electrons and quarks are "point particles". QFT has local field interactions "at a point", but the particles themselves always have wavefunctions with finite spatial support.

But does the wavefunction say anything about the size of the particles or just where they are most likely to be found?
 
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  • #18
  • #19
sujiwun said:
But does the wavefunction say anything about the size of the particles or just where they are most likely to be found?
Well it's their spatial probability density and from it you can derive expectations and statistics for observables. Anyway, no where does any QFT predict that electrons and quarks are point particles.
 
  • #20
dextercioby said:
Both point particles and fields (either classical or quantum) are not real. They're only models of our reality. Nothing but elements of a mathematical modelation of an experimentally observable reality.
In the same vein, even what is experimentally observable would be nothing but elements of a conceptual model of an otherwise completely incomprehensible reality.

Mathematical models at least have the advantage of being based on precise concepts.
Experimental concepts are precise only to the extent that they use the mathematical concepts.
 
  • #21
DarMM said:
Well it's their spatial probability density and from it you can derive expectations and statistics for observables. Anyway, no where does any QFT predict that electrons and quarks are point particles.

Then perhaps you can tell me what the radii are for quarks and electrons?

QFT may not predict that electrons and quarks are point particles, but, as far as I am aware it doesn't predict that they are not point particles either, and physics has no size for either of these.
 
  • #22
sujiwun said:
"The law of causality, I believe, like much that passes muster among philosophers, is a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm."

Bertrand Russell

Nice quote. One I appreciate. However, I would say that Russell was philosophizing, but doing a better job of it. Do you happen to know what publication was this from?
 
  • #23
Phrak said:
Nice quote. One I appreciate. However, I would say that Russell was philosophizing, but doing a better job of it. Do you happen to know what publication was this from?

Sorry, I can't recall where I first came across it - I just googled it.
 
  • #24
How can people state that virtual particles are not real? Of course they are real. They have calculatable effects on the energy levels of atoms. It is a small energy, but such an energy has been measured. How can you measure something that is not real?
 
  • #25
I'd say particles came from virtual particles. It is the only logical order, as it is with Chicken producing an egg.

Before any real matter was about, the vacuum was teeming with virtual particles. They live inside the vacuum, and is what makes up zero-point energy or even a Dirac sea if one can picture it.
 
  • #26
QuantumClue said:
I'd say particles came from virtual particles. It is the only logical order, as it is with Chicken producing an egg.

Before any real matter was about, the vacuum was teeming with virtual particles. They live inside the vacuum, and is what makes up zero-point energy or even a Dirac sea if one can picture it.

It strikes me that elementary particles such as electrons and quarks have no real existence of their own. They are essentially defined by their field effects, which are mediated by virtual particles.

No one has ever observed either, they have no descernible size, their existence is inferred from observed macroscopic effects. The same can be said of virtual particles of course, but, with both being mathematical models to help explain observable phenomena, I would suggest that virtual particles have primacy and it would be more sensible to look for a description of electrons and quarks in terms of virtual particles popping into and out of existence, than describe virtual particles in terms of what electrons and quarks are doing. Bottom up rather than top down.
 
  • #27
QuantumClue said:
How can people state that virtual particles are not real? Of course they are real.
Only people informed primarily by lay men's literature claim that. See Chapter A7 of my theoretical physics FAQ at http://arnold-neumaier.at/physfaq/physics-faq.html#A7 and the PF thread https://www.physicsforums.com/showthread.php?t=460685
QuantumClue said:
They have calculable effects on the energy levels of atoms. It is a small energy, but such an energy has been measured. How can you measure something that is not real?
The Casimir energy has been measured, not a virtual particle.
 
  • #28
sujiwun said:
Then perhaps you can tell me what the radii are for quarks and electrons?

QFT may not predict that electrons and quarks are point particles, but, as far as I am aware it doesn't predict that they are not point particles either, and physics has no size for either of these.
See the entry ''Are electrons pointlike/structureless?'' of Chapter B2 of my theoretical physics FAQ at http://arnold-neumaier.at/physfaq/physics-faq.html#pointlike
 
  • #29
A. Neumaier said:
Only people informed primarily by lay men's literature claim that. See Chapter A7 of my theoretical physics FAQ at http://arnold-neumaier.at/physfaq/physics-faq.html#A7 and the PF thread https://www.physicsforums.com/showthread.php?t=460685

The Casimir energy has been measured, not a virtual particle.

Well, aren't we just being a little pedantic however?

The Casimir Force, or more specifically the Lamb shift is caused by virtual particle energies. The Casimir force is in fact nothing more than an increasingly negative energy density between two plates in a vacuum via the interaction of virtual particles.

So I am interested how you can say what you say?
 
  • #30
QuantumClue said:
Well, aren't we just being a little pedantic however?
Didn't you complain about others being patronizing? Practice yourself what you preach!
QuantumClue said:
The Casimir Force, or more specifically the Lamb shift is caused by virtual particle energies.
No. http://lanl.arxiv.org/abs/hep-th/0503158 derives and calculates the Casimir effect without the use of virtual particles. Thus the latter cannot be their cause.
QuantumClue said:
So I am interested how you can say what you say?
I gave references for that. If you really are interested, read them!
 
  • #31
QuantumClue said:
Well, aren't we just being a little pedantic however?

The Casimir Force, or more specifically the Lamb shift is caused by virtual particle energies. The Casimir force is in fact nothing more than an increasingly negative energy density between two plates in a vacuum via the interaction of virtual particles.

So I am interested how you can say what you say?
You can derive the Casmir force nonperturbatively, in fact I think it's done in introductory textbooks like "Quantum Field Theory in a nutshell" by A. Zee. In such a derivation there are no "virtual particles".
 
  • #32
DarMM said:
You can derive the Casmir force nonperturbatively, in fact I think it's done in introductory textbooks like "Quantum Field Theory in a nutshell" by A. Zee. In such a derivation there are no "virtual particles".
That's true. In fact, I have never seen a derivation of the Casimir effect with virtual particles. The issue is not whether Casimir effect proves the reality of virtual particles (which it certainly doesn't), but whether it proves the reality of the zero-point energy (which is controversial, especially after the Jaffe's paper). Contrary to a frequent misconception, zero-point energy has absolutely nothing to do with virtual particles.
 
  • #33
For the last few posts, especially A. Neumaier's response, this is all down to interpretation.

Quantum mechanics directly predicted the existence of virtual particles long before any other explanations where concocted - and really were only created because certain scientists did not fully appreciate this existence which seems to have been for all practical terms, has been proven experimentally. Inviting new interpretations because people do not like the idea of virtual particles seems superfluous and redundant.
 
  • #34
  • #35
Demystifier said:
Contrary to a frequent misconception, zero-point energy has absolutely nothing to do with virtual particles.

You sure?

I'd agree that zero point energy ISN'T virtual particles and doesn't derive from virtual particles or what they are doing, but I wouldn't say it has nothing to do with them. More like the virtual particles are "anomalies" within the zero point energy field.
 
  • #36
Demystifier said:
The issue is not whether Casimir effect proves the reality of virtual particles (which it certainly doesn't), but whether it proves the reality of the zero-point energy (which is controversial, especially after the Jaffe's paper).

except that this guy has recorded it...

http://www.geo600.org/documents/audio-files

http://arxiv.org/PS_cache/arxiv/pdf/0709/0709.0611v1.pdf

http://en.wikipedia.org/wiki/GEO_600

http://www.fnal.gov/directorate/program_planning/Nov2009PACPublic/holometer-proposal-2009.pdf

http://holometer.fnal.gov/
 
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  • #37
sujiwun said:
You sure?

I'd agree that zero point energy ISN'T virtual particles and doesn't derive from virtual particles or what they are doing, but I wouldn't say it has nothing to do with them. More like the virtual particles are "anomalies" within the zero point energy field.

This is partially right. Zero point energy actually has a lot to do with our understanding of virtual particles when viewed as a vacuum which spontaneously bubbles energy at very small quantum levels. you try and remove all the energy from a part of space by cooling it down, you will never reach zero temperatures. What is left is an intrinsic energy which may as well be seen in terms of a virtual particle couldron boiling from the vacuum.
 
  • #38
sujiwun said:
how are imaginary virtual particles any different from imaginary electrons?

Do electrons actually exist?

According to the mainstream view, yes. Whereas virtual particles and imaginary electrons don't.
 
  • #39
A. Neumaier said:
According to the mainstream view, yes. Whereas virtual particles and imaginary electrons don't.

consensus reality - have you ever seen an electron, I know I haven't. It seems that scientists are just as capable of believing in their invisible imaginary friends as deists are, lol.

I've found reference to research on 'wet electrons' that claim to have isolated electrons in a sort of limbo state, but still no piccie.

For something to exist - in any meaningful sense - it ought to at least have a shape and definable size.

Now that doesn't dismiss the usefulness and validity of the concept of an electron within physics and its function in the world, but, by the same token, the usefulness and validity of virtual particles would be no less valid. If it works, use it.

Re: size of an electron.
This looked promising until I realizeed who the author was....lol.
http://prola.aps.org/abstract/PR/v14/i1/p20_1
 
  • #40
sujiwun said:
For something to exist - in any meaningful sense - it ought to at least have a shape and definable size.
Which is the size and shape of the wind? And of a collection of sea waves? So they don't exist?
 
  • #41
lightarrow said:
Which is the size and shape of the wind? And of a collection of sea waves? So they don't exist?

Yes, all very Taoist - but this just adds weight to my argument.

Does wind exist, really?

Waves can be defined as the propagation of information and energy, and in that sense be said to have real existence. Of course, you could carry the skepticism further and question whether energy itself exists - I mean seriously, is energy anything other than a mathematical abstraction - a conceptual map to model reality but not a reality in and of itself?

The mind carves experience up into perceived entities which we deem to "exist". Yes, you can say that ultimately, reality isn't a collection of "things" but a succession of processes/events. But still, we use signs and symbols to divide and represent those events as individual entities.

I started this thread with the question of whether virtual particles might be considered more fundamental than elementary particles? This was rejected on the grounds that virtual particles were mathematical constructs having no real existence but useful in modeling reality whereas electrons do have real existence irrespective of mathematical models of their nature.

I challenged that electrons have no more real existence than virtual particles, thus rendering them equivalent abstract constructs that may both be employed according to convenience and utility.

Here, in questioning the existence of wind, we take a Wittgensteinian view that nothing exists, and all is conceptual abstraction. True, possibly, but of little use.

So back to my original question, would it make more sense to consider electrons and quarks as products of the spontaneous emergent stochastic machinations of virtual particles briefly bursting forth from a chaotic quantum flux or to consider electrons and quarks as having fundamental existence that "produces" virtual force carrier particles in order to interact with each other?

Order(matter) as an essential component of chaos(space) rather than order as something other than chaos having "magical" properties that enables it to interact with itself.
 
  • #42
sujiwun said:
Yes, all very Taoist - but this just adds weight to my argument.

Does wind exist, really?

Waves can be defined as the propagation of information and energy, and in that sense be said to have real existence. Of course, you could carry the skepticism further and question whether energy itself exists - I mean seriously, is energy anything other than a mathematical abstraction - a conceptual map to model reality but not a reality in and of itself?

The mind carves experience up into perceived entities which we deem to "exist". Yes, you can say that ultimately, reality isn't a collection of "things" but a succession of processes/events. But still, we use signs and symbols to divide and represent those events as individual entities.

I started this thread with the question of whether virtual particles might be considered more fundamental than elementary particles? This was rejected on the grounds that virtual particles were mathematical constructs having no real existence but useful in modeling reality whereas electrons do have real existence irrespective of mathematical models of their nature.

I challenged that electrons have no more real existence than virtual particles, thus rendering them equivalent abstract constructs that may both be employed according to convenience and utility.

Here, in questioning the existence of wind, we take a Wittgensteinian view that nothing exists, and all is conceptual abstraction. True, possibly, but of little use.

So back to my original question, would it make more sense to consider electrons and quarks as products of the spontaneous emergent stochastic machinations of virtual particles briefly bursting forth from a chaotic quantum flux or to consider electrons and quarks as having fundamental existence that "produces" virtual force carrier particles in order to interact with each other?

Order(matter) as an essential component of chaos(space) rather than order as something other than chaos having "magical" properties that enables it to interact with itself.

With that kind of reasoning you could prove that nothing exist, and all. What if you pay for a house that doesn't actually exists and the seller tells you that it exists "virtually" in the net and so it exists? Would you feel satisfied of that answer?
 
  • #43
sujiwun said:
Then perhaps you can tell me what the radii are for quarks and electrons?

QFT may not predict that electrons and quarks are point particles, but, as far as I am aware it doesn't predict that they are not point particles either, and physics has no size for either of these.
Well for the electron one could always define the radius in a way related to the form factors. QFT says that electrons are not point particles, it explicitly predicts that. Any sensible meaning you can give to the word "point particle" is not obeyed by electrons in QFT. They are quanta of the field or quantum particles, separate notion from point particle.

Anyway, your talk of what is or isn't real (e.g. are biscuits real or just an abstraction of data received through our senses) is beside the point and distracts from the real issue of this thread. There is a difference between virtual particles and real particles. Real particles are eigenstates of the Hamiltonian and are predicted to exist by the theory. Virtual particles are simply labels on the internal lines of Feynman diagrams, which are themselves perturbative artefacts. QFT does not predict the existence of virtual particles, so according to the theory itself they are not real.
 
  • #44
What Are and Are-Not the characteristics of what are commonly referred to as a fundamental particles?

For the Are's, I get: mass, spin, charge, name, symbol, lepton number, quark number (maybe), family. To add to this, it's localizable. However, these are still idealized, on shell attributes. Anything else?

For the Are-Not's, I get: no size, no shape, no definite position, no definite momentum, not identifiable as a 'thing', and not identifiable as a 'particle'--whatever these mean.
 
  • #45
lightarrow said:
With that kind of reasoning you could prove that nothing exist, and all. What if you pay for a house that doesn't actually exists and the seller tells you that it exists "virtually" in the net and so it exists? Would you feel satisfied of that answer?

Exactly! Its all BS anyway, there is no wind, no house, no electron or virtual particles, just projections of abstract conceptions dreamt up by the fallible human mind. So if its all BS anyway, then why not go with the simplest GUT BS and make everything one, energy in physics, god in religion, consciousness in new age theosophy all the same none existent nonsense - so make determinism (matter) and indeterminism (quantum vacuum) one and the same, and build from the bottom up.
 
  • #46
sujiwun said:
Exactly! Its all BS anyway, there is no wind, no house, no electron or virtual particles, just projections of abstract conceptions dreamt up by the fallible human mind. So if its all BS anyway, then why not go with the simplest GUT BS and make everything one, energy in physics, god in religion, consciousness in new age theosophy all the same none existent nonsense - so make determinism (matter) and indeterminism (quantum vacuum) one and the same, and build from the bottom up.
And all this has to do with physics?
 
  • #47
lightarrow said:
And all this has to do with physics?

Do away with the particles and run with the quantum field.
 
  • #48
sujiwun said:
Do away with the particles and run with the quantum field.

Whilst it is an interpretation of physics, that our understanding is not really made of well-defined matter, where the world is intrinsically made up of probabilities - it's not a well-accepted view. It's very speculative to think nothing exists. It does not let you draw any conclusions on our existence, because existence would not exist! It must be true that what we have done is create and label a tool which is vast in its applications, and call it mathematics, and apply it to the working world. Our equations are not reality, this is true, but they help represent reality. While they are built on proposals based soley on mathematical knowledge, they do describe the physical world for us. There needs to be something out there, or there would be nothing to measure, right?
 
  • #49
sujiwun said:
consensus reality -

have you ever seen an electron, I know I haven't. It seems that scientists are just as capable of believing in their invisible imaginary friends as deists are, lol.

I've found reference to research on 'wet electrons' that claim to have isolated electrons in a sort of limbo state, but still no piccie.

For something to exist - in any meaningful sense - it ought to at least have a shape and definable size.

Now that doesn't dismiss the usefulness and validity of the concept of an electron within physics and its function in the world, but, by the same token, the usefulness and validity of virtual particles would be no less valid. If it works, use it.


http://prola.aps.org/abstract/PR/v14/i1/p20_1

great! good joke, a deep one ...lol...
consensus, mainstream view... ...lol...

like ants with sugar, running ! run madly
 
  • #50
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