Many-particle correlations in a non-equilibrium Luttinger liquid

We develop an operator-based approach to the problem of a Luttinger liquid conductor in a non-equilibrium stationary state. We show that the coherent-state many-body fermionic density matrix and all fermionic correlation functions out of equilibrium are given by one-dimensional functional determinants of the Fredholm type. Thus, the model constitutes a remarkable example of a many-body problem where all the correlation functions can be evaluated exactly. On the basis of the general formalism, we investigate four-point correlation functions of the fermions coming out of the Luttinger liquid wire. The correlations obtained among the fermionic distribution functions represent the combined effect of interaction and non-equilibrium conditions.