Speaker:Dr. Zhenning Cai (蔡振宁博士)

Time: 12:10-13:10, 20 October 2022 (Thursday) (Beijing time)

Tencent Meeting ID: 815-601-371

Venue: A103, Lijiao Building


Abstract

Lattice field theory is the lattice models of quantum field theory. The computation in lattice field theories often require taking high-dimensional ensemble averages. In some applications such as quantum chromodynamics with nonzero chemical potentials, the action functions may be complex, which leads to severe numerical sign problems when applying Monte Carlo methods, meaning that the variance of the numerial solution is significantly greater than its expectation. The complex Langevin method is one possible numerical approach to taming the numerical sign problem. However, the complex Langevin method often suffers from large biases or even divergence. Hence, regularization needs to be applied to this approach. In this talk, I will introduce a regularization method that adds a converging term to the action function and discuss methods to reduce the extra biases introduced by the regularization. Generalization of this approach to general SU(n) models will also be discussed in this talk.


About Dr. Cai

Zhenning Cai is an assistant professor at Department of Mathematics, National University of Singapore. Dr. Cai obtained his PhD Degree in Computational Mathematics from Peking University in 2013. From 2014 to 2015, he was sponsored by the Humboldt Foundation and worked as a postdoctoral researcher at RWTH Aachen University. In 2016, he worked at Duke University as a visiting assistant professor, after which he joined National University of Singapore in 2017. His research work covers areas including the modeling and simulation of gas kinetic theory and open quantum systems, as well as the complex Langevin method in quantum chromodynamics.