Intrinsic dissipative fluctuation rate in mesoscopic superconducting rings

The rate at which dissipative fluctuations occur in narrow superconducting rings is considered within the Little-Langer-Ambegaokar-McCumber-Halperin framework. The mesoscopic regime, in which the ring circumference L does not greatly exceed the correlation length ξ, is specifically addressed. In this regime, significant differences arise between models that mimic voltage and current sources, the former (latter) exhibiting corrections to the fluctuation rate algebraic in ξ/L (exponentially small in L/ξ). The theory employs Forman's elaboration of the Gel'fand-Yaglom technique for computing fluctuation determinants.