Polyakov loop effects on the phase diagram in strong-coupling lattice QCD

TL;DR

This paper explores how Polyakov loop fluctuations influence the QCD phase diagram in strong-coupling lattice QCD, revealing their significant impact on transition temperatures and the interplay between chiral and deconfinement transitions.

Contribution

It introduces a detailed analysis of Polyakov loop effects using strong-coupling expansion and Weiss mean-field approximation, highlighting their role in the phase structure.

Findings

Polyakov loops suppress the chiral transition temperature at small chemical potential.

They cause a significant increase in the interaction measure near the chiral transition.

No separate deconfinement transition boundary is observed from the chiral boundary in Weiss MFA.

Abstract

We investigate the Polyakov loop effects on the QCD phase diagram by using the strong-coupling (1/g^2) expansion of the lattice QCD (SC-LQCD) with one species of unrooted staggered quark, including O}(1/g^4) effects. We take account of the effects of Polyakov loop fluctuations in Weiss mean-field approximation (MFA), and compare the results with those in the Haar-measure MFA (no fluctuation from the mean-field). The Polyakov loops strongly suppress the chiral transition temperature in the second-order/crossover region at small chemical potential, while they give a minor modification of the first-order phase boundary at larger chemical potential. The Polyakov loops also account for a drastic increase of the interaction measure near the chiral phase transition. The chiral and Polyakov loop susceptibilities have their peaks close to each other in the second-order/crossover region. In particular in Weiss MFA, there is no indication of the separated deconfinement transition boundary from the chiral phase boundary at any chemical potential. We discuss the interplay between the chiral and deconfinement dynamics via the bare quark mass dependence of susceptibilities.