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We calculate the finite-temperature density and polarization equations of state of one-dimensional fermions with a zero-range interaction, considering both attractive and repulsive regimes. In the path-integral formulation of the…

Quantum Gases · Physics 2018-09-19 Andrew C. Loheac , Jens Braun , Joaquín E. Drut

We study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion and choosing Polyakov type of loops as the main dynamical variables representing the fermionic matter. To get a first…

High Energy Physics - Lattice · Physics 2008-11-26 R. De Pietri , A. Feo , E. Seiler , I. -O. Stamatescu

The sign problem of QCD prevents standard lattice simulations to determine the phase diagram of strong interactions with a finite chemical potential directly. Complex Langevin simulations provide an alternative method to sample path…

High Energy Physics - Lattice · Physics 2015-06-09 Gert Aarts , Felipe Attanasio , Benjamin Jäger , Erhard Seiler , Dénes Sexty , Ion-Olimpiu Stamatescu

Recent progress of the complex Langevin method and the Lefschetz thimble in connection with the sign problem is reviewed. These methods rely on the complexification of the original field manifold and they allow direct simulations of…

High Energy Physics - Lattice · Physics 2014-12-01 Denes Sexty

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

Heavy-Dense QCD (HDQCD) is a popular theory to investigate the sign problem in quantum field theory. Besides its physical applications, HDQCD is relatively easy to implement numerically: the fermionic degrees of freedom are integrated out,…

High Energy Physics - Lattice · Physics 2016-11-07 Nicolas Garron , Kurt Langfeld

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

We study the deconfinement transition line in QCD for quark chemical potentials up to $\mu_q \sim 5 T$ ($\mu_B \sim 15 T$). To circumvent the sign problem we use the complex Langevin equation with gauge cooling. The plaquette gauge action…

High Energy Physics - Lattice · Physics 2020-08-05 M. Scherzer , D. Sexty , I. -O. Stamatescu

The complex Langevin method is a leading candidate for solving the sign problem occurring in various physical situations, notably QCD at finite chemical potential. Its most vexing problem is `convergence to the wrong limit', where the…

High Energy Physics - Lattice · Physics 2011-10-27 Gert Aarts , Frank A. James , Erhard Seiler , Ion-Olimpiu Stamatescu

Using combined strong coupling and hopping parameter expansions, we derive an effective three-dimensional theory from thermal lattice QCD with heavy Wilson quarks. The theory depends on traced Polyakov loops only and correctly reflects the…

High Energy Physics - Lattice · Physics 2012-01-27 Michael Fromm , Jens Langelage , Stefano Lottini , Owe Philipsen

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 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

We present an application of the standard Langevin dynamics to the problem of weak coupling perturbative expansions for Lattice QCD. This method can be applied to the computation of the most general observables. In this preliminary work we…

High Energy Physics - Lattice · Physics 2009-09-25 Francesco Di Renzo , Giuseppe Marchesini , Paolo Marenzoni , Enrico Onofri

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

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

Simulations of QCD with a finite chemical potential typically lead to a severe sign problem, prohibiting any standard Monte Carlo approach. Complex Langevin simulations provide an alternative to sample path integrals with oscillating weight…

High Energy Physics - Lattice · Physics 2014-11-12 Gert Aarts , Felipe Attanasio , Benjamin Jäger , Erhard Seiler , Denes Sexty , Ion-Olimpiu Stamatescu

The sign problem appears in lattice QCD as soon as a non-zero chemical potential is introduced. This prevents direct simulations to determine the phase structure of the strongly interacting matter. Complex Langevin methods have been…

High Energy Physics - Lattice · Physics 2018-04-18 Felipe Attanasio , Benjamin Jäger

We propose various improvements of finite step-size updating for full QCD on the lattice that might turn finite step-size updating into a viable alternative to the hybrid Monte Carlo algorithm. These improvements are noise reduction of the…

High Energy Physics - Lattice · Physics 2009-10-31 M. Hasenbusch

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 study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion and choosing Polyakov-type loops as the main dynamical variables representing the fermionic matter. This model still…

High Energy Physics - Lattice · Physics 2009-04-14 R. De Pietri , A. Feo , E. Seiler , I. -O. Stamatescu