Nonlinear quantum transport and current noise

We study nonequilibrium transport and noise in a generic dissipative tight- binding model. Within a real-time path integral approach, we derive formall y exact series expressions in the number of tunneling events for the noise valid for arbitrary bias, frequency and temperature. At zero temperature, t he low-frequency noise can be summed in analytic form. The resulting Shiba- like \omega \-singularity is a consequence of the 1/t(2) decay law for the current correlation function. At finite temperature, this singularity is sm oothed out.