Two complex problems on the lattice: transport coefficients and finite chemical potential

TL;DR

This paper discusses recent advances in calculating transport coefficients and handling complex actions in lattice QCD, demonstrating that stochastic quantization and complex Langevin dynamics effectively address the sign problem at finite chemical potential.

Contribution

It introduces the application of stochastic quantization and complex Langevin dynamics to complex action lattice theories, showing they overcome the sign problem even in the thermodynamic limit.

Findings

Sign problem does not hinder complex Langevin methods at finite chemical potential.

Initial results show successful extraction of transport coefficients from lattice QCD.

Comparison of models illustrates the approach's effectiveness in different systems.

Abstract

After a few remarks about the problem of extracting transport coefficients from lattice QCD calculations, I report on recent developments in applying stochastic quantization and complex Langevin dynamics to field theories with a complex action due to a nonzero chemical potential. First results demonstrate that the sign problem poses no obstacle for this approach, even in the thermodynamic limit. I conclude with a comparison of two simple one-link models, describing a euclidean system at finite chemical potential and a Minkowski system in real time.