[zakk]

Protons are non-perturbative, indeed, but this does not mean that there are no virtual particles exchanged inside a proton. It seems like your comment implies that, sorry if I misunderstood.

On the contrary, this means that there are too many virtual particles (gluons) being exchanged inside a proton, so many that perturbation theory is not applicable.

[hither_shores]

Virtual particles are part of an indexing scheme for perturbation series - saying that you leave the perturbative regime when you have "too many" of them is like saying that crystalline solids melt when they have too many normal modes.

[xigency]

Finally an analogy where I understand neither comparison :)

[AnimalMuppet]

Are gluons virtual? (Or are they virtual inside a proton?)

[cwillu]

Your question is can be posed as “is there a well-behaved resonance of the gluon field in a proton, that lasts long enough for it to be identified”. It's kinda like identifying a bubble in a pot of cold water vs a pot just starting to boil vs a rolling boil.

[frutiger]

Gluons are real.