Semiclassical Theory of Bardeen-Cooper-Schrieffer Pairing-Gap Fluctuations
uperfluidity and superconductivity are genuine many-body manifestations of quantum coherence. For finite-size systems the associated pairing gap fluctuates as a function of size or shape. We provide a theoretical description of the zero temperature pairing fluctuations in the weak-coupling BCS limit of mesoscopic systems characterized by order or chaos dynamics. The theory accurately describes exp