Impact of vector-current interactions on the QCD phase diagram

TL;DR

This study explores how nonderivative vector-current interactions influence the QCD phase diagram, revealing their effects on the chiral phase transition and critical points at real and imaginary chemical potentials.

Contribution

It introduces a nonlocal Polyakov-loop-extended Nambu--Jona-Lasinio model to analyze vector-current interactions' impact on the QCD phase diagram, especially at the Roberge-Weiss endpoint.

Findings

Vector interactions sharpen the RW transition at the endpoint.

Critical points shift towards lower temperatures with stronger vector coupling.

Conditions for transition disappearance into a crossover are discussed.

Abstract

Using a nonlocal version of the Polyakov-loop-extended Nambu--Jona-Lasinio model, we investi- gate effects of a nonderivative vector-current interaction (relating to the quark-number density) at both real and imaginary chemical potentials. This repulsive vector interaction between quarks has the following impact on the chiral first-order phase transition: at imaginary chemical potential it sharpens the transition at the Roberge-Weiss (RW) end point and moves this critical point toward lower temperatures; at real chemical potential, the critical end point moves on a trajectory towards larger chemical potentials and lower temperatures with increasing vector coupling strength. The conditions are discussed at which the first-order phase transition disappears and turns into a smooth crossover.