Current fluctuation in an ideally conducting ring
Lesovik G. B.
It is shown that in the noninteracting-electron approximation an ideally conducting ring manifests nonergodicity. In equilibrium with zero average current the current-current correlation function does not decay with time. When the interaction with the reservoir is taken into account explicitly, ergodicity is restored and the decay time of the correlation function is determined by the broadening of the discrete levels.