A Model for QCD at High Density and Large Quark Mass

TL;DR

This paper develops an effective model for high-density QCD using a hopping parameter expansion and Polyakov loops, analyzing phase structure and transitions at non-zero chemical potential.

Contribution

It introduces a novel effective model for high-density QCD that incorporates fermionic matter via Polyakov loops and explores its phase structure through analytical and numerical methods.

Findings

Model exhibits a sign problem at non-zero chemical potential.

Phase transitions and crossovers are characterized by charge density and diquark susceptibility.

Results provide insights into the behavior of QCD at high baryonic density.

Abstract

We study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion and choosing Polyakov type of loops as the main dynamical variables representing the fermionic matter. To get a first idea of the phase structure, the model is analyzed in strong coupling expansion and using a mean field approximation. In numerical simulations, the model still shows the so-called sign problem, a difficulty peculiar to non-zero chemical potential, but it permits the development of algorithms which ensure a good overlap of the Monte Carlo ensemble with the true one. We review the main features of the model and present calculations concerning the dependence of various observables on the chemical potential and on the temperature, in particular of the charge density and the diquark susceptibility, which may be used to characterize the various phases expected at high baryonic density. We obtain in this way information about the phase structure of the model and the corresponding phase transitions and cross over regions, which can be considered as hints for the behaviour of non-zero density QCD.