Quarks: Confinement Issues & Free Particles

[Bready]

I'm struggling to get to grips with the idea that quarks cannot be observed as isolated particles due to confinement and yet existed as free particles during an early epoch after the big bang. Surely quarks aren't actually confined if they can exist at high enough energies.

In fact aren't these:

http://en.wikipedia.org/wiki/Quark-gluon_plasma

observations of free quarks? How is confinement being violated in these cases?

 

[K.J.Healey]

You can't be too strict on your definition of "free". Is an electron in a metal, moving around on in the conduction band "free"? Well it can move around yes, but it is still subject to the potentials around it. Same with the QGP, they're not free in the sense that there is one particle, subject to no external influence. They are just compressed so much that there is no distinguished boundaries of the "baryons" everything overlaps and so can move as a plasma/soup.

 

[malawi_glenn]

Well you can compare this (i think) with aysompotic freedom of QCD, at high momentum transfer, quarks are "almost" free, the coupling decreases as energy scale increases. This is why quark-gluon plasma can occur.