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QCD at nonzero baryon chemical potential suffers from the sign problem, due to the complex quark determinant. Complex Langevin dynamics can provide a solution, provided certain conditions are met. One of these conditions, holomorphicity of…

High Energy Physics - Lattice · Physics 2017-06-07 Gert Aarts , Erhard Seiler , Denes Sexty , Ion-Olimpiu Stamatescu

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…

High Energy Physics - Lattice · Physics 2018-04-18 D. K. Sinclair , J. B. Kogut

We present the results of continuum-extrapolated lattice simulations of quantum chromodynamics (QCD) above the crossover temperature and for unprecedentedly high baryon densities at the physical point, employing the complex Langevin…

High Energy Physics - Lattice · Physics 2026-04-22 Michael Mandl , Dénes Sexty , Daniel Unterhuber

We simulate lattice QCD at finite quark-number chemical potential, $\mu$, using the complex-Langevin equation (CLE) with gauge-cooling and adaptive updating to prevent instabilities. The CLE is used because QCD at finite $\mu$ has a complex…

High Energy Physics - Lattice · Physics 2018-10-30 D. K. Sinclair , J. B. Kogut

Lattice QCD at non-vanishing chemical potential is studied using the complex Langevin equation (CLE). One of the conditions for the correctness of the results of the CLE is that the zeroes of the measure coming from the fermionic…

High Energy Physics - Lattice · Physics 2016-11-10 G. Aarts , E. Seiler , D. Sexty , I. -O. Stamatescu

Recently, the complex Langevin method has been applied successfully to finite density QCD either in the deconfinement phase or in the heavy dense limit with the aid of a new technique called the gauge cooling. In the confinement phase with…

High Energy Physics - Lattice · Physics 2016-08-24 Keitaro Nagata , Jun Nishimura , Shinji Shimasaki

It is well known that investigating QCD at finite density by standard Monte Carlo methods is extremely difficult due to the sign problem. Some years ago, the complex Langevin method with gauge cooling was shown to work at high temperature,…

High Energy Physics - Lattice · Physics 2019-01-15 Keitaro Nagata , Jun Nishimura , Shinji Shimasaki

Complex Langevin simulations have been able to successfully reproduce results from Monte Carlo methods in the region where the sign problem is mild and make predictions when it is exponentially hard. We present here our study of the QCD…

High Energy Physics - Lattice · Physics 2016-10-25 Gert Aarts , Felipe Attanasio , Benjamin Jäger , Dénes Sexty

The sign problem at nonzero chemical potential prohibits the use of importance sampling in lattice simulations. Since complex Langevin dynamics does not rely on importance sampling, it provides a potential solution. Recently it was shown…

High Energy Physics - Lattice · Physics 2015-06-12 Gert Aarts , Frank A. James , Jan M. Pawlowski , Erhard Seiler , Denes Sexty , Ion-Olimpiu Stamatescu

We present the reweighted complex Langevin method, which enlarges the applicability range of the complex Langevin method by reweighting the complex trajectories. In this reweighting procedure both the auxiliary and target ensembles have a…

High Energy Physics - Lattice · Physics 2017-01-06 Jacques Bloch , Johannes Meisinger , Sebastian Schmalzbauer

A method is developed which speeds up averaging in quantum simulations where minus signs cause difficulties. A Langevin equation method in conjunction with a replication algorithm is used enabling one to average over a continuously varying…

comp-gas · Physics 2009-10-22 J. M. Deutsch

Some recent developments to handle the numerical sign problem in QCD and related theories at nonzero density are reviewed. In this contribution I focus on changing the integration order to soften the severity of the sign problem, the…

High Energy Physics - Lattice · Physics 2015-02-13 Gert Aarts

A nonperturbative lattice study of QCD at finite chemical potential is complicated due to the complex fermion determinant and the sign problem. Here we apply the method of stochastic quantization and complex Langevin dynamics to this…

High Energy Physics - Lattice · Physics 2009-02-09 Gert Aarts , Ion-Olimpiu Stamatescu

Monte Carlo studies of QCD at finite density suffer from the sign problem, which becomes easily uncontrollable as the chemical potential $\mu$ is increased even for a moderate lattice size. In this work we make an attempt to approach the…

High Energy Physics - Lattice · Physics 2018-12-06 Yuta Ito , Hideo Matsufuru , Jun Nishimura , Shinji Shimasaki , Asato Tsuchiya , Shoichiro Tsutsui

We present a method of simulating lattice QCD at nonzero chemical potential in the chiral limit. By adding a weak four-fermi interaction to the standard staggered fermion SU(3) QCD action, we produce an algorithm in which the limit of…

High Energy Physics - Lattice · Physics 2009-10-28 I. M. Barbour , S. E. Morrison , John B. Kogut

We study complex Langevin simulations of a toy model as well as QCD, supplemented with a dynamical stabilization (DS) term, which was proposed to regularize the complexified process at lower temperatures. We compare the results to…

High Energy Physics - Lattice · Physics 2024-06-03 Michael W. Hansen , Dénes Sexty

In the landscape of approaches toward the simulation of Lattice Models with complex action the Complex Langevin (CL) appears as a straightforward method with a simple, well defined setup. Its applicability, however, is controlled by certain…

High Energy Physics - Lattice · Physics 2018-04-18 Gert Aarts , Kirill Boguslavski , Manuel Scherzer , Erhard Seiler , Dénes Sexty , Ion-Olimpiu Stamatescu

We study a random matrix model for QCD at finite density via complex Langevin dynamics. This model has a phase transition to a phase with nonzero baryon density. We study the convergence of the algorithm as a function of the quark mass and…

High Energy Physics - Lattice · Physics 2017-04-05 Jacques Bloch , Jonas Glesaaen , Owe Philipsen , Jacobus Verbaarschot , Savvas Zafeiropoulos

The complex Langevin (CL) method is a promising approach to overcome the sign problem, which emerges in real-time formulations of quantum field theories. Over the past decade, stabilization techniques for CL have been developed with…

High Energy Physics - Lattice · Physics 2022-10-18 Kirill Boguslavski , Paul Hotzy , David I. Müller

We study the Stephanov model, which is an RMT model for QCD at finite density, using the Complex Langevin algorithm. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory rather than to…

High Energy Physics - Lattice · Physics 2018-04-18 Jacques Bloch , Jonas Glesaaen , Jacobus Verbaarschot , Savvas Zafeiropoulos