Revisiting strong coupling QCD at finite temperature and baryon density

TL;DR

This paper explores the phase diagram of lattice QCD at strong coupling and finite density, using advanced Monte Carlo techniques to address computational challenges and comparing results with mean-field predictions.

Contribution

It introduces improved simulation methods for strong coupling lattice QCD at finite density and provides updated phase diagram results, highlighting discrepancies with previous mean-field analyses.

Findings

Significant corrections to previous phase diagram results.

Discrepancies of order 10 in critical point location compared to mean-field.

Effective control of the sign problem at finite density.

Abstract

The strong coupling limit ($\beta_{gauge}=0$) of lattice QCD with staggered fermions enjoys the same non-perturbative properties as continuum QCD, namely confinement and chiral symmetry breaking. In contrast to the situation at weak coupling, the sign problem which appears at finite density can be brought under control for a determination of the full (mu,T) phase diagram by Monte Carlo simulations. Further difficulties with efficiency and ergodicity of the simulations, especially at the strongly first-order, low-T, finite-mu transition, are addressed respectively with a worm algorithm and multicanonical sampling. Our simulations reveal sizeable corrections to the old results of Karsch and Muetter. Comparison with analytic mean-field determinations of the phase diagram shows discrepancies of O(10) in the location of the QCD critical point.