Quantum Brownian motion. II

This paper generalizes some previous results presented in Gaioli et al. [In t. J. Theor. Phys. 36, 2167 (1997)]. We evaluate the autocorrelation functi on of the stochastic acceleration and study the asymptotic evolution of the mean occupation number of a harmonic oscillator playing the role of a Brow nian particle. We also analyze some deviations from the Bose population at low temperatures and compare it with the deviations from the exponential de cay law of an unstable quantum system.