QUANTUM DISSIPATION AND QUANTUM-NOISE

We derive the exact action for a damped mechanical system (and the spe cial case of the linear oscillator) from the path integral formulation of the quantum Brownian motion problem developed by Schwinger and by Feynman and Vernon. The doubling of the phase-space degrees of freedom for dissipative systems and thermal field theories is discussed and t he initial values of the doubled variables are related to quantum nois e effects. (C) 1995 Academic Press, Inc.