  The analytic continuation from the Euclidean domain to real space of the
one-particle irreducible quantum effective action is discussed in the context
of generalized local equilibrium states. Discontinuous terms associated with
dissipative behavior are parametrized in terms of a conveniently defined sign
operator. A generalized variational principle is then formulated, which allows
to obtain causal and real dissipative equations of motion from the analytically
continued quantum effective action. Differential equations derived from the
implications of general covariance determine the space-time evolution of the
temperature and fluid velocity fields and allow for a discussion of entropy
production including a local form of the second law of thermodynamics.
