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 [ital L] does not greatly exceed the correlation length [xi], 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 [xi]/[ital L] (exponentially small in [ital L]/[xi]). The theory employs Forman's elaboration of the Gel'fand-Yaglom technique for computing fluctuation determinants.