Chiral phase boundary of QCD at finite temperature

We analyze the approach to chiral symmetry breaking in QCD at finitetemperature, using the functional renormalization group. We compute the runninggauge coupling in QCD for all temperatures and scales within a simple truncatedrenormalization flow. At finite temperature, the coupling is governed by afixed point of the 3-dimensional theory for scales smaller than thecorresponding temperature. Chiral symmetry breaking is approached if therunning coupling drives the quark sector to criticality. We quantitativelydetermine the phase boundary in the plane of temperature and number of flavorsand find good agreement with lattice results. As a generic and testableprediction, we observe that our underlying IR fixed-point scenario leaves itsimprint in the shape of the phase boundary near the critical flavor number:here, the scaling of the critical temperature is determined by thezero-temperature IR critical exponent of the running coupling.Comment: 39 pages, 8 figure