Speaker
Description
Lattice simulations have clearly established that the low- and high-temperature regimes of QCD are controlled by distinct active degrees of freedom, hadrons on the one side, and quarks and gluons on the other side. Yet, many continuum studies of the confinement/deconfinement transition rely on the Polyakov loop which measures how energetically costly it is to bring an external quark probe into a bath of quarks and gluons. In the low temperature phase, this energy cost is very large which one interprets as the system being confined. Yet this energy cost is finite which seems to indicate that bringing a quark probe remains possible, in blatant tension with the change in degrees of freedom referred to above. We resolve this tension by studying the net quark number of the bath as one brings an external quark probe into the medium. We show that, while in the deconfined phase, the net quark number gained by the system is equal to the quark number of the probe, in line with the idea that, in this phase, one can bring a quark without significantly affecting the bath, in the confined phase, the net quark number gained by the system is equal to 0 or 3 (depending on the chemical potential), which we interpret as the medium forming either mesons or baryons to screen the quark probe.