Average phase factor in the PNJL model

TL;DR

This paper evaluates the average phase factor in the PNJL model at finite chemical potential, revealing its dependence on the Polyakov loop and implications for lattice QCD feasibility and the critical endpoint location.

Contribution

It introduces the impact of scalar-type eight-quark interactions on the phase structure and the critical endpoint in the PNJL model at finite density.

Findings

Average phase factor is finite only when Polyakov loop > 0.5 at high chemical potential.

The scalar eight-quark interaction shortens the distance of the CEP to the phase boundary.

The model reproduces lattice QCD data below critical temperature for low chemical potential.

Abstract

The average phase factor of the QCD determinant is evaluated at finite quark chemical potential ({\mu}_q) with the two-flavor version of the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with the scalar-type eight-quark interaction. For {\mu}_q larger than half the pion mass at vacuum m_{\pi}, the average phase factor is finite only when the Polyakov loop is larger than 0.5, indicating that lattice QCD is feasible only in the deconfinement phase. A critical endpoint (CEP) lies in the region of the zero average phase factor. The scalar-type eight-quark interaction makes it shorter a relative distance of the CEP to the boundary of the region. For {\mu}_q < m_{\pi}/2, the PNJL model with dynamical mesonic fluctuations can reproduce lattice QCD data below the critical temperature.