Complex Langevin dynamics and other approaches at finite chemical potential

TL;DR

This paper reviews the sign problem in lattice QCD at finite density, explores methods to mitigate it, and discusses the potential of complex Langevin dynamics for nonzero chemical potential scenarios.

Contribution

It provides a comprehensive review of approaches to handle the sign problem, including effective models and the prospects of complex Langevin dynamics.

Findings

Sign problem varies in severity across models

Effective 3D models can be solved with different methods

Complex Langevin dynamics shows promise for nonzero density

Abstract

I review the presence of the sign problem in lattice QCD at nonzero baryon density and its relation with the overlap and Silver Blaze problems. I then discuss progress in some cases where the sign problem can be handled, either because the sign problem is absent or because it is milder than in full QCD. Some time is spent on effective three-dimensional models, which can be treated with a variety of methods. I conclude with a discussion of the applicability of complex Langevin dynamics at nonzero density.