Really Computing Non-perturbative Real Time Correlation Functions

TL;DR

This paper proposes a modified classical simulation algorithm for real-time correlation functions at high temperature, incorporating an effective Hamiltonian with an ultraviolet cutoff to address divergences and better determine baryon violation rates.

Contribution

It introduces a new algorithm using the hard thermal loop Hamiltonian with an ultraviolet cutoff to improve the calculation of real-time correlation functions in thermal quantum field theory.

Findings

Addresses ultraviolet divergence issues in classical simulations.

Proposes a cutoff-dependent algorithm aiming for cutoff independence.

Aims to accurately determine baryon violation rates at high temperature.

Abstract

It has been argued by Grigoriev and Rubakov that one can simulate real time processes involving baryon number non-conservation at high temperature using real time evolution of classical equations, and summing over initial conditions with a classical thermal weight. It is known that such a naive algorithm is plagued by ultraviolet divergences. In quantum theory the divergences are regularized, but the corresponding graphs involve the contributions from the hard momentum region and also the new scale $\sim gT$ comes into play. We propose a modified algorithm which involves solving the classical equations of motion for the effective hard thermal loop Hamiltonian with an ultraviolet cutoff $\mu \gg gT$ and integrating over initial conditions with a proper thermal weight. Such an algorithm should provide a determination of the infrared behavior of real time correlation function $<Q(t) Q(0)>_T$ determining the baryon violation rate. Hopefully, the results obtained in this modified algorithm would be cutoff-independent.