Chicken or the Egg

sujiwun

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?

A. Neumaier

Chicken. See http://www.physicsforums.com/showthread.php?t=460685

sujiwun

perhaps neither....
http://en.wikipedia.org/wiki/Point_particle

Dmitry67

Interpretation dependent

Phrak

What does 'cause' mean?

K^2

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.

DarMM

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.

sujiwun

"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

sujiwun

Are the electrons and quarks, that all matter is made of - being point particles, by definition having no spatial extension - any more real?

Dmitry67

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.

sujiwun

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

dextercioby

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.

sujiwun

http://www.library.yale.edu/libraryn...s-une-pipe.jpg

DarMM

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.

DarMM

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.

dextercioby

I sense some irony. Anyways, the difference is that a pipe is something real. A point particle is not.

sujiwun

But does the wavefunction say anything about the size of the particles or just where they are most likely to be found?