The Problem of Ground State in Thermo-Field Dynamics

Abstract

Analytic continuation of quantum statistical physics from imaginary to real time is analyzed. Adiabatic vanishing of interactions at real time infinities gives origin to singularities at complex times. This undermines the hypothesis of decoupling of interactions at $t\to \infty$. Hence an interacting thermal vacuum is a necessary component of the exact real-time formalism. Consequences for Thermo-field dynamics are discussed.

8pp. Latex file with 4 Latex figures incorporated. (Talk given at 3rd Workshop on Thermal Field Theories, August 1993, Banff, Canada.)