Auxiliary field Monte-Carlo study of the QCD phase diagram at strong coupling

TL;DR

This study employs an auxiliary field Monte-Carlo method to explore the QCD phase diagram at strong coupling, revealing a reduced transition temperature and an extended hadron phase compared to mean field results.

Contribution

The paper introduces a novel AFMC approach to study the QCD phase diagram at strong coupling, addressing the sign problem and comparing results with mean field approximations.

Findings

Transition temperature reduced by ~10%.

Hadron phase extended by ~20% in chemical potential.

Sign problem manageable on small lattices.

Abstract

We investigate the QCD phase diagram in the strong coupling limit by using a newly developed auxiliary field Monte-Carlo (AFMC) method. Starting from an effective action in the leading order of the 1/g^2 and 1/d expansion with one species of unrooted staggered fermion, we solve the many-body problem exactly by introducing the auxiliary fields and integrating out the temporal links and quark fields. We have a sign problem in AFMC, which is different from the original one in finite density lattice QCD. For low momentum auxiliary field modes, a complex phase cancellation mechanism exists, and the sign problem is not serious on a small lattice. Compared with the mean field results, the transition temperature is found to be reduced by around 10 % and the hadron phase is found to be extended in the larger chemical potential direction by around 20 %, as observed in the monomer-dimer-polymer (MDP) simulations.