Spectral splits of neutrinos as a BCS-BEC crossover type phenomenon

Abstract

We show that the spectral split of a neutrino ensemble, which initially consists of electron type neutrinos, is analogous to the Bardeen-Cooper-Schrieffer-Bose-Einstein condensate (BCS-BEC) crossover already observed in ultracold atomic gas experiments. Such a neutrino ensemble mimics the deleptonization burst of a core collapse supernova. Although these two phenomena belong to very different domains of physics, the propagation of neutrinos from highly interacting inner regions of the supernova to the vacuum is reminiscent of the evolution of Cooper pairs between weak and strong interaction regimes during the crossover. The Hamiltonians and the corresponding many-body states undergo very similar transformations if one replaces the pair quasispin of the latter with the neutrino isospin of the former.