Could High Energy Virtual Particles Destroy a Starship?

[Ken G]

OK, a lot of good points are being made. A particularly important one would seem to be that electric forces are only mediated by virtual photons in some gauges-- this was interpreted above as indications they are "not real." There are several problems with using this to dismiss taking virtual particles seriously as ontological constructs:
1) virtual particles are not claimed to be real, they are claimed to be virtual. This means they seek a new ontological status that normal standards of "realness" cannot be applied to. That seems obvious, but is getting overlooked.
2) virtual particles that mediate forces like the one corresponding to the Coulomb potential are gauge bosons, so it is perhaps not surprising they are not present in all gauges. The purpose of a gauge is not to make a claim on reality, it is to make a calculation simpler. It might well be argued the same can be said about physics in its entirety (echoing qsa above). So although it is useful to establish that virtual photons can be done away with in certain gauges, the question that remains is whether or not we gain access to certain forms of computational convenience by choosing a gauge that supports such gauge boson activity, at the conceptual level. Is anything in physics theory not at the conceptual level, after all?

So anyway, I'm not advocating for the reality of virtual particles, we shouldn't even call them virtual were that the attitude. I'm merely questioning whether or not it really makes consistent logical sense to imagine that physics supports a clear line between what is real and what is just a mathematical trick in some theory. We use any foothold we can get when trying to interpret and understand reality, and we cannot be burdened by the need to make the case that any ontological entity we invoke is "actually real."

 

[Ken G]

When we glance at the sun, do we see "real" photons? Griffiths suggests: not exactly, but they are darn close.

Yes, I think I am very much on Griffiths' page here, that's a nice quote. The point is, when we do physics, we make all kinds of choices about what we care about and what we don't. Those choices will have as much an influence on what we regard as real as what is "actually real." In particular, the former has a clear-cut meaning, and the latter does not.

So far the jet experiments are the closest we have to detecting "real" gluons; the jet gluons are close enough to being on-shell that they form collimated jets when they decay. But, like the neutrinos and photons, they are really only "almost real".

I'd say you've really set the discussion on its ear-- we were debating whether there is actually any such thing as virtual particles, and you are making a strong case that we should really be asking whether there is actually any such thing as real particles. Coup de grace.

The patter that connects the collection of Feynman diagrams to an experimental result is just an imperfect way to express the relation of mathematics to reality.

Spoken like a true empiricist. I think it's times like this that the gap between empiricist views and rationalist views really creates communication barriers, it's just as well that physics proceeds without reaching resolution of this kind of issue.

 

[Mordred]

Spoken like a true empiricist. I think it's times like this that the gap between empiricist views and rationalist views really creates communication barriers, it's just as well that physics proceeds without reaching resolution of this kind of issue.

LOL I had a math professor once state that mathematics is the only universal lanquage, that may be true but it certainly has many dialects and interpretations.

I like this site as an excellent and simple explanation of virtual particles for the novice
It doesn't swamp one with formulas or complex lanquage. I personally think that the term "intermediate particle " or something similar would have led to greater overall acceptance than the usage of the word virtual. Granted this site doesn't present the full picture but it often is useful in explaining the concept to the novice.

http://www2.slac.stanford.edu/vvc/theory/virtual.html
http://www2.slac.stanford.edu/vvc/theory/quantum.html

edit: I also found this article was informative and useful in the past

http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html

I posted these to aid understanding to the beginners that frequent this site tidbits like tthese have proven useful in the past so I gathered a collection of em currently around 4 giga bytes worth lol

 

[bbbeard]

Even though perturbative quantum field theory has proven to be extremely successful, the lack of a proper non-perturbative theory is kind of unsatisfying.

You should look into what's going on in lattice gauge theory. For example, check out http://pdg.lbl.gov/2011/reviews/rpp2011-rev-ckm-matrix.pdf" . Scroll through and see how lattice gauge theory is used to produce estimates of important physical quantities.

While there is no doubt that lattice methods are not as well-developed as perturbative QFT, they don't suffer the same limitations in the strong-coupling regime...

 

[bbbeard]

I'd say you've really set the discussion on its ear-- we were debating whether there is actually any such thing as virtual particles, and you are making a strong case that we should really be asking whether there is actually any such thing as real particles. Coup de grace.

It seems to me there are a number of situations like this in physics. Are you familiar with the "thermodynamic limit"? The theory of phase transitions in thermodynamics, it turns out, really only works for infinite systems, or more precisely, in that limit. So we can reasonably ask whether the water boiling on the stove is "really boiling" or just "virtually boiling"...

 

[Mordred]

bbbreard do you happen to know of a good site that teaches the Cabibbo-Kobayashi-Maskawa (CKM) matrix? If so I would be highly interested I use standard matrix calculations regularly however the standard 3 degrees of motion matrixes used in engineering which are limitted in that they do not include the time dimension if you happen to know of a means to describe a 4-d matrix I would be highly interested in how its derived and used. I would also be interested in virtual boiling and the phase transitions in thermodynamics my first impulse is the transitory point from one state to another where additional energy is needed to change from solid to liquid etc but these are new terms to me so am probably wrong on that score lol.

 

[bbbeard]

bbbreard do you happen to know of a good site that teaches the Cabibbo-Kobayashi-Maskawa (CKM) matrix? If so I would be highly interested I use standard matrix calculations regularly however the standard 3 degrees of motion matrixes used in engineering which are limitted in that they do not include the time dimension if you happen to know of a means to describe a 4-d matrix I would be highly interested in how its derived and used. I would also be interested in virtual boiling and the phase transitions in thermodynamics my first impulse is the transitory point from one state to another where additional energy is needed to change from solid to liquid etc but these are new terms to me so am probably wrong on that score lol.

The CKM matrix is a 3x3 matrix that relates the strong (i.e. QCD) eigenstates of the down, strange, and bottom quarks to the weak eigenstates of the same quarks.

One of the little-publicized quirks of the Standard Model is that the down particle in QCD is slightly different from the down particle in the weak interactions. Ditto strange and bottom. The free parameters in the CKM matrix (three Cabibbo angles and a phase factor) are some of the plethora of free parameters in the Standard Model.

If you want to learn more, just google "CKM matrix"... ;-)

 

[Vanadium 50]

CKM matrix? This has gone way far afield of the original question.