Chiral phase transition at finite temperature and conformal dynamics in large Nf QCD

We investigate the chiral phase transition at finite temperature (T) in colour SU(N-c = 3) Quantum Chromodynamics (QCD) with a variable number of fermions N-f in the fundamental representation by using lattice QCD. For N-f = 6 we study the approach to asymptotic scaling by considering lattices with several temporal extensions N-t. We then extract the dimensionless ratio T-c/Lambda(L) (Lambda(L) = lattice Lambda-parameter) for N-f = 6 and N-f = 8, the latter relying on our earlier results. Further, we collect the (pseudo) critical couplings beta(c)(L). for the chiral phase transition at N-f = 0 (quenched), and N-f = 4 at a fixed N-t = 6. The results are consistent with enhanced fermionic screening at larger N-f. The ratio T-c/Lambda(L) depends very mildly on N-f in the N-f = 0-4 region, starts increasing at N-f = 6, and becomes significantly larger at N-f = 8, close to the edge of the conformal window. We discuss interpretations of these results as well as their possible interrelation with preconformal dynamics in the light of a functional renormalization group analysis. (C) 2012 Elsevier B.V. All rights reserved.