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

TL;DR

This study explores the finite-temperature chiral phase transition in large Nf QCD using lattice simulations, revealing how the transition behavior varies with Nf and approaching the conformal window.

Contribution

It provides new lattice QCD results for Nf=6 and 8, analyzing the scaling and critical couplings related to the chiral transition near the conformal window.

Findings

Tc/Lambda_L increases significantly at Nf=8

Results suggest enhanced fermionic screening at larger Nf

Transition behavior approaches conformal dynamics near Nf=8

Abstract

We investigate the chiral phase transition at finite temperature (T) in colour SU(Nc=3) Quantum Chromodynamics (QCD) with six species of fermions (Nf=6) in the fundamental representation by using lattice QCD with improved staggered fermions. By considering lattices with several temporal extensions Nt, we observe asymptotic scaling for Nt > 4. We then extract the dimensionless ratio Tc/Lambda_L (Lambda_L = Lattice Lambda-parameter) for Nf = 6 and Nf = 8, the latter relying on our earlier results. Further, we collect the critical couplings beta^c for the chiral phase transition at Nf = 0 (quenched), and Nf = 4 at a fixed Nt = 6. The results are consistent with enhanced fermionic screening at larger Nf. The Tc/Lambda_L depends very mildly on Nf in the Nf = 0 - 4 region, starts increasing at Nf = 6, and becomes significantly larger at Nf = 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.