SHORT-TIME BEHAVIOR OF THE CORRELATION-FUNCTIONS FOR THE QUANTUM LANGEVIN EQUATION

We analyze the quantum Langevin equation obtained for the Ford-Kac-Maz ur and related models. We study an explicit expression for the correla tion function of the noise, obtained by making use of the normal-order ed product of operators. Such an expression is divergence-free, does n ot require any frequency cutoff, and yields the classical (Markoffian) case in the limit of vanishing h. We also bring to light and discuss two different regimes for the momentum autocorrelation. The high-tempe rature and weak-coupling limits are considered, and the latter is show n to be related to van Hove's ''lambda(2)T'' Limit.