  We extend the work of Kurchan on the Gallavotti-Cohen fluctuation theorem,
which yields a symmetry property of the large deviation function, to general
Markov processes. These include jump processes describing the evolution of
stochastic lattice gases driven in the bulk or through particle reservoirs,
general diffusive processes in physical and/or velocity space, as well as
Hamiltonian systems with stochastic boundary conditions. For dynamics
satisfying local detailed balance we establish a link between the action
functional of the fluctuation theorem and the entropy production. This gives,
in the linear regime, an alternative derivation of the Green-Kubo formula and
the Onsager reciprocity relations. In the nonlinear regime consequences of the
new symmetry are harder to come by and the large derivation functional
difficult to compute. For the asymmetric simple exclusion process the latter is
determined explicitly using the Bethe ansatz in the limit of large N.
