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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

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

The real time evolution of a scalar field in 0+1 dimensions is investigated on a complex time contour. The path integral formulation of the system has a sign problem, which is circumvented using the Complex Langevin equation. Measurement of…

High Energy Physics - Lattice · Physics 2023-09-13 Nina Maria Lampl , Dénes Sexty

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

The nuclear shell model is known to describe the properties of various nuclei extremely well. However, the auxiliary-field quantum Monte Carlo calculations cannot be applied to it with general interactions due to the sign problem. The model…

Nuclear Theory · Physics 2025-08-22 Yuhma Asano , Yuta Ito , Jun Nishimura , Noritaka Shimizu

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

The complex Langevin method is one hopeful candidate to tackle the sign problem. This method is applicable not only to QCD but also to nonrelativistic field theory, such as condensed matter physics. We present the simulation results of a…

High Energy Physics - Lattice · Physics 2015-08-04 Arata Yamamoto , Tomoya Hayata

The ability to describe strongly interacting matter at finite temperature and baryon density provides the means to determine, for instance, the equation of state of QCD at non-zero baryon chemical potential. From a theoretical point of…

High Energy Physics - Lattice · Physics 2019-01-30 Felipe Attanasio , Benjamin Jäger

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

Monte Carlo simulation of gauge theories with a $\theta$ term is known to be extremely difficult due to the sign problem. Recently there has been major progress in solving this problem based on the idea of complexifying dynamical variables.…

High Energy Physics - Lattice · Physics 2020-05-08 Mitsuaki Hirasawa , Akira Matsumoto , Jun Nishimura , Atis Yosprakob

Abelian and non-Abelian gauge theories are of central importance in many areas of physics. In condensed matter physics, Abelian U(1) lattice gauge theories arise in the description of certain quantum spin liquids. In quantum information…

Quantum Physics · Physics 2015-06-15 U. -J. Wiese

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

Using complex Langevin method we probe the possibility of dynamical supersymmetry breaking in supersymmetric quantum mechanics models with complex actions. The models we consider are invariant under the combined operation of parity and time…

High Energy Physics - Lattice · Physics 2021-11-10 Anosh Joseph , Arpith Kumar

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

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

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

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

Centre-stabilised $SU(N)$ Yang-Mills theories on $\mathbb{R}^3 \times S^1$ are QCD-like theories that can be engineered to remain weakly-coupled at all energy scales by taking the $S^1$ circle length $L$ to be sufficiently small. In this…

High Energy Physics - Theory · Physics 2023-03-27 John Lai

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

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