Abstract
Starting from the usual formulation of nonequilibrium quantum statistical mechanics, the expectation value of an operator A in a steady state nonequilibrium quantum system is shown to have the form 〈A〉 =Tr{A} /Tr{}, where H is the Hamiltonian, β is the inverse of the temperature, and Y is an operator which depends on how the system is driven out of equilibrium. Because 〈A〉 is not expressed as a sum of correlation functions integrated over real time, one can now consider performing nonperturbative calculations in interacting nonequilibrium quantum problems.
- Received 28 May 1992
DOI:https://doi.org/10.1103/PhysRevLett.70.2134
©1993 American Physical Society