Complex Langevin simulation of QCD at finite density and low temperature using the deformation technique

¹ Center of Medical Information Science, Kochi Medical School, Kochi University
² KEK Theory Center, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan
³ Department of Particle and Nuclear Physics, School of High Energy Accelerator Science, Graduate University for Advanced Studies (SOKENDAI), Tsukuba 305-0801, Japan
⁴ Research and Education Center for Natural Sciences, Keio University, Hiyoshi 4-1-1, Yokohama, Kanagawa 223-8521, Japan

^* Speaker, e-mail: shinji.shimasaki@keio.jp

Published online: 26 March 2018

Abstract

We study QCD at finite density and low temperature by using the complex Langevin method. We employ the gauge cooling to control the unitarity norm and intro-duce a deformation parameter in the Dirac operator to avoid the singular-drift problem. The reliability of the obtained results are judged by the probability distribution of the magnitude of the drift term. By making extrapolations with respect to the deformation parameter using only the reliable results, we obtain results for the original system. We perform simulations on a 4³ × 8 lattice and show that our method works well even in the region where the reweighing method fails due to the severe sign problem. As a result we observe a delayed onset of the baryon number density as compared with the phase-quenched model, which is a clear sign of the Silver Blaze phenomenon.