Theta vacuum and entanglement interaction in the three-flavor Polyakov-loop extended Nambu-Jona-Lasinio model

TL;DR

This paper explores how theta-vacuum effects influence the QCD phase diagram in a 2+1 flavor system using the PNJL and entanglement PNJL models, revealing sharper chiral transitions and first-order transitions at large theta.

Contribution

It introduces the impact of theta-vacuum effects on the QCD phase diagram within the PNJL framework and proposes a method to bypass the lattice QCD sign problem at finite theta.

Findings

Theta-vacuum effects sharpen the chiral transition.

Large theta induces first-order chiral transition at zero chemical potential.

A proposed method to circumvent the lattice QCD sign problem at finite theta.

Abstract

We investigate theta-vacuum effects on the QCD phase diagram for the realistic 2+1 flavor system, using the three-flavor Polyakov-extended Nambu-Jona-Lasinio (PNJL) model and the entanglement PNJL model as an extension of the PNJL model. The theta-vacuum effects make the chiral transition sharper. For large theta-vacuum angle the chiral transition becomes first order even if the quark number chemical potential is zero, when the entanglement coupling between the chiral condensate and the Polyakov loop is taken into account. We finally propose a way of circumventing the sign problem on lattice QCD with finite theta.