CORRELATION-FUNCTIONS FOR MESOSCOPIC CONDUCTANCE AT FINITE FREQUENCY

We extend to finite frequency the calculation of the conductance corre lation function for a mesoscopic device, using linear-response theory for noninteracting electrons. Because the conductance is complex, two functions are required to fully specify correlations in the real and i maginary parts. The two functions have different frequency dependences due to the placement of the diffusion propagators in the simplest dia gram. We apply our results to the case of h/e conductance oscillations in a ring.