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Lattice simulations of non-zero density QCD introduce the so-called sign problem (complex or negative probabilities), which invalidates importance sampling methods. To circumvent this, we use the Complex Langevin Equation (CLE), to measure…

High Energy Physics - Lattice · Physics 2023-03-01 Michael W. Hansen , Dénes Sexty

The complex Langevin method (CLM) is a promising tool to address the sign problem in quantum field theories with complex actions. However, it can converge to incorrect results even when simulations appear stable, highlighting the need for…

High Energy Physics - Lattice · Physics 2026-03-27 Anosh Joseph , Arpith Kumar

We study the mechanism of the gauge cooling technique to stabilize the complex Langevin method in the one-dimensional periodic setting. In this case, we find the exact solutions for the gauge transform which minimizes the Frobenius norm of…

Numerical Analysis · Mathematics 2020-04-22 Zhenning Cai , Yana Di , Xiaoyu Dong

The complex Langevin method (CLM) offers a potential solution to the sign problem in quantum field theories with complex actions, but can converge to incorrect results even when simulations appear stable. Existing diagnostics monitor drift…

High Energy Physics - Lattice · Physics 2025-10-30 Anosh Joseph , Arpith Kumar

Recently the complex Langevin method (CLM) has been attracting attention as a solution to the sign problem, which occurs in Monte Carlo calculations when the effective Boltzmann weight is not real positive. An undesirable feature of the…

High Energy Physics - Lattice · Physics 2018-06-13 Keitaro Nagata , Jun Nishimura , Shinji Shimasaki

This review explores the Complex Langevin Method (CLM), a stochastic quantization technique designed to address the sign problem in quantum field theories with complex actions. Beginning with foundational principles, the review examines the…

High Energy Physics - Lattice · Physics 2025-04-04 Anosh Joseph , Arpith Kumar

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 Complex Langevin (CL) method sometimes shows convergence to the wrong limit, even though the Schwinger-Dyson Equations (SDE) are fulfilled. We analyze this problem in a more general context for the case of one complex variable. We prove…

Mathematical Physics · Physics 2018-12-17 Lorenzo Luis Salcedo , Erhard Seiler

The method of complex Langevin simulations is a tool that can be used to tackle the complex-action problem encountered, for instance, in finite-density lattice quantum chromodynamics or real-time lattice field theories. The method is based…

High Energy Physics - Lattice · Physics 2024-10-18 Michael Mandl , Michael W. Hansen , Erhard Seiler , Dénes Sexty

Progress in the application of the complex Langevin method to full QCD at non-zero chemical potential is reported. The method evades the sign problem which makes naive simulations at nonzero density impossible. The procedure 'gauge cooling'…

High Energy Physics - Lattice · Physics 2015-06-22 Denes Sexty

Non-perturbative formulations of field theories are essential to capture intriguing physical phenomena, including confinement in QCD, spontaneous supersymmetry breaking, and dynamical compactification in superstrings. Lattice regularization…

High Energy Physics - Lattice · Physics 2023-09-08 Arpith Kumar

The great majority of algorithms employed in the study of lattice field theory are based on Monte Carlo's importance sampling method, i.e. on probability interpretation of the Boltzmann weight. Unfortunately in many theories of interest one…

High Energy Physics - Lattice · Physics 2016-06-03 Lorenzo Bongiovanni

The complex Langevin method, a numerical method used to compute the ensemble average with a complex partition function, often suffers from runaway instability. We study the regularization of the complex Langevin method via augmenting the…

Computational Physics · Physics 2022-02-09 Zhenning Cai , Yang Kuang , Hong Kiat Tan

The complex Langevin method in conjunction with the gauge cooling is applied to the two-dimensional lattice $SU(2)$ Yang-Mills theory that is analytically solvable. We obtain strong numerical evidence that at large Langevin time the…

High Energy Physics - Lattice · Physics 2015-10-21 Hiroki Makino , Hiroshi Suzuki , Daisuke Takeda

Langevin Monte Carlo (LMC) is an iterative algorithm used to generate samples from a distribution that is known only up to a normalizing constant. The nonasymptotic dependence of its mixing time on the dimension and target accuracy is…

Machine Learning · Statistics 2020-02-26 Niladri S. Chatterji , Jelena Diakonikolas , Michael I. Jordan , Peter L. Bartlett

The complex Langevin (CL) method shows great promise in enabling the calculation of observables for theories with complex actions. Nevertheless, real-time quantum field theories have remained largely unsolved due to the particular severity…

High Energy Physics - Lattice · Physics 2024-01-12 Kirill Boguslavski , Paul Hotzy , David I. Müller

We investigate a simple model using the numerical simulation in the complex Langevin equation (CLE) and the analytical approximation with the Gaussian Ansatz. We find that the Gaussian Ansatz captures the essential and even quantitative…

High Energy Physics - Lattice · Physics 2016-12-07 Yuya Abe , Kenji Fukushima

We apply the complex Langevin method (CLM) to overcome the sign problem in 4D SU(2) gauge theory with a theta term extending our previous work on the 2D U(1) case. The topology freezing problem can be solved by using open boundary…

High Energy Physics - Lattice · Physics 2021-12-06 Akira Matsumoto , Kohta Hatakeyama , Mitsuaki Hirasawa , Masazumi Honda , Yuta Ito , Jun Nishimura , Atis Yosprakob

A key task in Bayesian statistics is sampling from distributions that are only specified up to a partition function (i.e., constant of proportionality). However, without any assumptions, sampling (even approximately) can be #P-hard, and few…

Machine Learning · Computer Science 2018-12-03 Rong Ge , Holden Lee , Andrej Risteski

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