Neutrino oscillations in gravitational and cosmological backgrounds

TL;DR

This paper investigates how gravitational and scalar perturbations in spacetime backgrounds cause phase shifts in neutrino oscillations, with implications for observations at cosmological distances.

Contribution

It introduces an eikonal approximation method to quantify phase shifts in neutrino oscillations caused by gravitational and scalar perturbations in flat and FRW spacetimes.

Findings

Phase shifts are small but persist at large redshifts.

Results depend on perturbation characteristics.

Order-of-magnitude estimates provided.

Abstract

We use the eikonal approximation in order to calculate the additional phase shift between two neutrino mass eigenstates during their propagation in a background of gravitational wave or scalar perturbations in the flat and the FRW spacetime metric. We comment on the dependence of the results on the characteristics of the perturbations, give some order-of-magnitude estimates, and find that, although small, the resulting phase difference persists for large redshifts, up to the validity of our approximations.