Complex Langevin dynamics for dynamical QCD at nonzero chemical potential: a comparison with multi-parameter reweighting

TL;DR

This paper compares complex Langevin dynamics and multi-parameter reweighting methods for lattice QCD at nonzero chemical potential, finding good agreement on fine lattices but breakdown on coarser ones, with implications for simulations.

Contribution

It provides a systematic comparison between complex Langevin and reweighting approaches in lattice QCD at finite chemical potential, highlighting their regimes of validity.

Findings

Good agreement between methods on lattices below 0.15 fm

Breakdown of complex Langevin on coarser lattices

Investigation of rooting effects with two flavors

Abstract

We study lattice QCD at non-vanishing chemical potential using the complex Langevin equation. We compare the results with multi-parameter reweighting both from $\mu=0$ and phase quenched ensembles. We find a good agreement for lattice spacings below $\approx$0.15 fm. On coarser lattices the complex Langevin approach breaks down. Four flavors of staggered fermions are used on $N_t=4, 6$ and 8 lattices. For one ensemble we also use two flavors to investigate the effects of rooting.