Classical Real Time Correlation Functions And Quantum Corrections at Finite Temperature

We consider quantum corrections to classical real time correlation functions at finite temperature. We derive a semi-classical expansion in powers of $\hbar$ with coefficients including all orders in the coupling constant. We give explicit expressions up to order $\hbar^2$. We restrict ourselves to a scalar theory. This method, if extended to gauge theories, might be used to compute quantum corrections to the high temperature baryon number violation rate in the Standard Model.