Effective potential approach to quantum dissipation in condensed matter systems

The effects of dissipation on the thermodynamic properties of nonlinear quantum systems are approached by the path-integral method in order to construct approximate classical-like formulas for evaluating thermal averages of thermodynamic quantities. Explicit calculations are presented for one-particle and many-body systems. The effects of the dissipation mechanism on the phase diagram of two-dimensional Josephson arrays is discussed.Comment: 7 pages, 5 figures, to appear in the Proceedings of Nonlinearity, Integrability And All That 20 Years After Needs 7