Really computing nonperturbative real time correlation functions.

Abstract

It has been argued by Grigoriev and Rubakov that one can simulate real time processes involving baryon number nonconservation 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 \ensuremath{\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 \ensuremath{\mu}\ensuremath{\gg}gT and integrating over initial conditions with a proper thermal weight. Such an algorithm should provide a determination of the infrared behavior of the real time correlation function 〈Q(t)Q(0)${\mathrm{〉}}_{\mathit{T}}$ determining the baryon violation rate. Hopefully, the results obtained in this modified algorithm will be cutoff independent.