Probing deconfinement in a chiral effective model with Polyakov loop at imaginary chemical potential

TL;DR

This paper investigates the phase structure of a Polyakov-loop extended Nambu-Jona-Lasinio model at finite temperature and imaginary chemical potential, highlighting the confinement-deconfinement transition characteristics and their dependence on model parameters.

Contribution

It introduces a new parameter to characterize the confinement-deconfinement transition and analyzes how the phase structure depends on the Polyakov loop potential and fermion coupling.

Findings

Confined phase shows a cos(3μ_I/T) dependence of the chiral condensate.

Deconfined phase exhibits a cos(μ_I/T) dependence with a cusp at the Z(3) transition.

Critical endpoint location can be shifted into real chemical potential by adjusting the fermion coupling G_s.

Abstract

The phase structure of the two-flavor Polyakov-loop extended Nambu-Jona-Lashinio model is explored at finite temperature and imaginary chemical potential with a particular emphasis on the confinement-deconfinement transition. We point out that the confined phase is characterized by a $\cos3\mu_I/T$ dependence of the chiral condensate on the imaginary chemical potential while in the deconfined phase this dependence is given by $\cos\mu_I/T$ and accompanied by a cusp structure induced by the Z(3) transition. We demonstrate that the phase structure of the model strongly depends on the choice of the Polyakov loop potential $\mathcal{U}$. Furthermore, we find that by changing the four fermion coupling constant $G_s$, the location of the critical endpoint of the deconfinement transition can be moved into the real chemical potential region. We propose a new parameter characterizing the confinement-deconfinement transition.