Simulating a CP-violating topological term in gauge theories

TL;DR

This paper investigates the theta-dependence of SU(N) gauge theories, using Monte Carlo simulations at imaginary theta to understand their scaling behavior and estimate expansion coefficients related to CP violation.

Contribution

It provides new numerical evidence of scaling in the continuum limit and accurately estimates expansion coefficients up to O(theta^6) for the first time.

Findings

Good evidence of scaling in the continuum limit

Accurate estimates of theta expansion coefficients up to O(theta^6)

Describes the imaginary theta dependence of the ground-state energy

Abstract

We present recent results on the theta-dependence of four-dimensional SU(N) gauge theories, where theta is the coefficient of the CP-violating topological term in the Lagrangian. In particular, we study the scaling behavior of these theories, by Monte Carlo simulations at imaginary theta. The numerical results provide good evidence of scaling in the continuum limit. The imaginary theta dependence of the ground-state energy turns out to be well described by the first few terms of related expansions around theta=0, providing accurate estimates of the first few coefficients, up to O(theta^6).