EPJ Web of Conferences 175, 07031 (2018)
https://doi.org/10.1051/epjconf/201817507031

Complex Langevin Simulations of QCD at Finite Density – Progress Report

¹ HEP Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
² Department of Energy, Division of High Energy Physics, Washington, DC 20585, USA
³ Department of Physics – TQHN, University of Maryland, 82 Regents Drive, College Park, MD 20742, USA

^* Speaker, e-mail: dks@hep.anl.gov This research was supported in part by US Department of Energy contract DE-AC02-06CH11357

Published online: 26 March 2018

Abstract

We simulate lattice QCD at finite quark-number chemical potential to study nuclear matter, using the complex Langevin equation (CLE). The CLE is used because the fermion determinant is complex so that standard methods relying on importance sampling fail. Adaptive methods and gauge-cooling are used to prevent runaway solutions. Even then, the CLE is not guaranteed to give correct results. We are therefore performing extensive testing to determine under what, if any, conditions we can achieve reliable results. Our earlier simulations at β = 6/g² = 5.6, m = 0.025 on a 12⁴ lattice reproduced the expected phase structure but failed in the details. Our current simulations at β = 5.7 on a 16⁴ lattice fail in similar ways while showing some improvement. We are therefore moving to even weaker couplings to see if the CLE might produce the correct results in the continuum (weak-coupling) limit, or, if it still fails, whether it might reproduce the results of the phase-quenched theory. We also discuss action (and other dynamics) modifications which might improve the performance of the CLE.