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Monte Carlo methods cannot probe far into the QCD phase diagram with a real chemical potential, due to the famous sign problem. Complex Langevin simulations, using adaptive step-size scaling and gauge cooling, are suited for sampling path…

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

We consider a generalized Thirring model in 0+1 dimensions at finite density. In order to deal with the resulting sign problem we employ stochastic quantization, i.e., a complex Langevin evolution. We investigate the convergence properties…

High Energy Physics - Lattice · Physics 2013-05-23 Jan M. Pawlowski , Christian Zielinski

One reason for the well known fact that the Complex Langevin (CL) method sometimes fails to converge or converges to the wrong limit has been identified long ago: it is insufficient decay of the probability density either near infinity or…

High Energy Physics - Lattice · Physics 2020-01-15 M. Scherzer , E. Seiler , D. Sexty , I. -O. Stamatescu

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 discuss the design of an invariant measure-preserving transformed dynamics for the numerical treatment of Langevin dynamics based on rescaling of time, with the goal of sampling from an invariant measure. Given an appropriate monitor…

Numerical Analysis · Mathematics 2024-08-30 Alix Leroy , Benedict Leimkuhler , Jonas Latz , Desmond J. Higham

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 demonstrate analytically that complex Langevin dynamics can solve the sign problem in one-dimensional QCD in the thermodynamic limit. In particular, it is shown that the contributions from the complex and highly oscillating spectral…

High Energy Physics - Lattice · Physics 2014-11-21 Gert Aarts , K. Splittorff

Complex Langevin simulations are an attempt to solve the sign (or complex-action) problem encountered in various physical systems of interest. The method is based on a complexification of the underlying degrees of freedom and an evolution…

High Energy Physics - Lattice · Physics 2025-04-08 Michael W. Hansen , Michael Mandl , Erhard Seiler , Dénes Sexty

Self-interacting scalar quantum field theories possessing $PT$-symmetry are physically admissible since their energy spectrum is real and bounded below. However, models with $PT$-invariant potentials can have complex actions in general and…

High Energy Physics - Lattice · Physics 2022-01-31 Arpith Kumar , Anosh Joseph

Complex Langevin dynamics can be used to perform numerical simulations of theories with a complex action. In order to justify the procedure, it is important to understand the properties of the real and positive distribution, which is…

High Energy Physics - Lattice · Physics 2013-09-13 Pietro Giudice , Gert Aarts , Erhard Seiler

We show that complex Langevin simulation converges to a wrong result, by relating it to the Lefschetz-thimble path integral, when the path-integral weight has different phases among dominant complex saddle points. Equilibrium solution of…

High Energy Physics - Lattice · Physics 2017-02-07 Tomoya Hayata , Yoshimasa Hidaka , Yuya Tanizaki

QCD at finite quark-/baryon-number density, which describes nuclear matter, has a sign problem which prevents direct application of standard simulation methods based on importance sampling. When such finite density is implemented by the…

High Energy Physics - Lattice · Physics 2016-11-09 D. K. Sinclair , J. 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

Latent variable models are widely used in social and behavioural sciences, including education, psychology, and political science. With the increasing availability of large and complex datasets, high-dimensional latent variable models have…

Computation · Statistics 2025-12-09 Motonori Oka , Yunxiao Chen , Irini Moustaki

In complex Langevin simulations, the insufficient decay of the probability density near infinity leads to boundary terms that spoil the formal argument for correctness. We present a formulation of this term that is cheaply measurable in…

High Energy Physics - Lattice · Physics 2021-12-07 Michael W. Hansen , Erhard Seiler , Dénes Sexty , Ion-Olimipu Stamatescu

The theoretical treatment of Fermi systems consisting of particles with unequal masses is challenging. Even in one spatial dimension analytic solutions are limited to special configurations and numerical progress with Monte Carlo…

Quantum Gases · Physics 2018-07-19 Lukas Rammelmüller , Joaquín E. Drut , Jens Braun

One of the yet unsolved questions of QCD in the context of the Standard Model is to explain the strong CP problem. A way to look for a better understanding of it is to investigate the theory in the presence of a non-zero topological theta…

High Energy Physics - Lattice · Physics 2014-11-05 Lorenzo Bongiovanni , Gert Aarts , Erhard Seiler , Denes Sexty

In this paper, we characterize the synchronization phenomenon of hyperchaotic scalar non-linear delay dynamics in a fully-developed chaos regime. Our results rely on the observation that, in that regime, the stationary statistical…

Chaotic Dynamics · Physics 2008-10-08 Adrian A. Budini

We present results on the ballistic and diffusive behavior of the Langevin dynamics in a periodic potential that is driven away from equilibrium by a space-time periodic driving force, extending some of the results obtained by Collet and…

Mathematical Physics · Physics 2015-06-19 R. Joubaud , G. Pavliotis , G. Stoltz

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