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In this paper we test the complex Langevin algorithm for numerical simulations of a random matrix model of QCD with a first order phase transition to a phase of finite baryon density. We observe that a naive implementation of the algorithm…

High Energy Physics - Lattice · Physics 2018-04-04 J. Bloch , J. Glesaaen , J. J. M. Verbaarschot , S. Zafeiropoulos

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

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 method has been attracting much attention as a solution to the sign problem since the method was shown to work in finite density QCD in the deconfined phase by using the so-called gauge cooling procedure. Whether it…

High Energy Physics - Lattice · Physics 2015-11-30 Keitaro Nagata , Jun Nishimura , Shinji Shimasaki

We study full QCD at finite density and low temperature with light quark mass using the complex Langevin method. Since the singular drift problem turns out to be mild on a $4^3 \times 8$ lattice we use, the gauge cooling is performed only…

High Energy Physics - Lattice · Physics 2016-11-28 Keitaro Nagata , Hideo Matsufuru , Jun Nishimura , Shinji Shimasaki

Recently there has been remarkable progress in the complex Langevin method, which aims at solving the complex action problem by complexifying the dynamical variables in the original path integral. In particular, a new technique called the…

High Energy Physics - Lattice · Physics 2015-12-30 Keitaro Nagata , Jun Nishimura , Shinji Shimasaki

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 introduce a deformation parameter in the Dirac operator to avoid the singular-drift…

High Energy Physics - Lattice · Physics 2018-04-18 Keitro Nagata , Jun Nishimura , Shinji Shimasaki

Complex Langevin simulations provide an alternative to sample path integrals with complex weights and therefore are suited to determine the phase diagram of QCD from first principles. Adaptive step-size scaling and gauge cooling are used to…

High Energy Physics - Lattice · Physics 2015-11-02 Gert Aarts , Felipe Attanasio , Benjamin Jäger , Erhard Seiler , Dénes Sexty , Ion-Olimpiu Stamatescu

Complex Langevin simulations allow numerical studies of theories that exhibit a sign problem, such as QCD, and are thereby potentially suitable to determine the QCD phase diagram from first principles. Here we study QCD in the limit of…

High Energy Physics - Lattice · Physics 2016-10-12 Gert Aarts , Felipe Attanasio , Benjamin Jäger , Dénes Sexty

We present our results obtained from gauge cooled complex Langevin simulations in 1+1d QCD at non-zero densities in the strong coupling regime with unrooted staggered fermions. For small quark masses there are regions of the chemical…

High Energy Physics - Lattice · Physics 2016-11-03 Sebastian Schmalzbauer , Jacques Bloch

We first test the Complex Langevin method (CLE) on various simple models. We then introduce the method of Gauge Cooling to control the dynamics of the process and ensure thin distributions in the imaginary direction. We finally apply CLE…

High Energy Physics - Lattice · Physics 2013-10-29 Gert Aarts , Lorenzo Bongiovanni , Erhard Seiler , Denes Sexty , Ion-Olimpiu Stamatescu

At nonzero chemical potential the numerical sign problem in lattice field theory limits the use of standard algorithms based on importance sampling. Complex Langevin dynamics provides a possible solution, but it has to be applied with care.…

High Energy Physics - Lattice · Physics 2015-06-15 Gert Aarts , Lorenzo Bongiovanni , Erhard Seiler , Denes Sexty , Ion-Olimpiu Stamatescu

QCD at non-zero chemical potential ($\mu$) for quark number has a complex fermion determinant and thus standard simulation methods for lattice QCD cannot be applied. We therefore simulate this theory using the Complex-Langevin algorithm…

High Energy Physics - Lattice · Physics 2015-10-22 D. K. Sinclair , J. B. Kogut

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

We employ a new method, "gauge cooling", to stabilize complex Langevin simulations of QCD with heavy quarks. The results are checked against results obtained with reweigthing; we find agreement within the estimated errors. The method allows…

High Energy Physics - Lattice · Physics 2015-06-12 Erhard Seiler , Dénes Sexty , Ion-Olimpiu Stamatescu

The complex Langevin method is a promising approach to the complex-action problem based on a fictitious time evolution of complexified dynamical variables under the influence of a Gaussian noise. Although it is known to have a restricted…

High Energy Physics - Lattice · Physics 2017-01-04 Keitaro Nagata , Jun Nishimura , Shinji Shimasaki

We present our latest results on the application of the complex Langevin method to one- and two-dimensional QCD. Although the method is stable, it unfortunately converges to an incorrect result when applied as such. After applying…

High Energy Physics - Lattice · Physics 2015-08-24 Jacques Bloch , Johannes Mahr , Sebastian Schmalzbauer

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

Complex Langevin simulations provide an alternative to sample path integrals with complex weights and therefore are suited to determine the phase diagram of QCD from first principles. We use our proposed method of Dynamic Stabilisation (DS)…

High Energy Physics - Lattice · Physics 2016-07-20 Gert Aarts , Felipe Attanasio , Benjamin Jäger , Dénes Sexty

In this review we present the current state-of-the-art on complex Langevin simulations and their implications for the QCD phase diagram. After a short summary of the complex Langevin method, we present and discuss recent developments. Here…

High Energy Physics - Lattice · Physics 2020-10-28 Felipe Attanasio , Benjamin Jäger , Felix P. G. Ziegler
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