On finite-temperature holographic QCD in the Veneziano limit

A bstract Holographic models in the T = 0 universality class of QCD in the limit of large number N c of colors and N f massless fermion flavors, but constant ratio x f = N f /N c , are analyzed at finite temperature. The models contain a 5-dimensional metric and two scalars, a dilaton sourcing Tr F 2 and a tachyon dual to q̄q . The phase structure on the T, x f plane is computed and various 1st order, 2nd order transitions and crossovers with their chiral symmetry properties are identified. For each x f , the temperature dependence of p/T 4 and the condensate q̄q is computed. In the simplest case, we find that for x f up to the critical x c ~ 4 there is a 1st order transition on which chiral symmetry is broken and the energy density jumps. In the conformal window x c < x f < 11 / 2, there is only a continuous crossover between two conformal phases. When approaching x c from below, x f → x c , temperature scales approach zero as specified by Miransky scaling.