Sterile Neutrino Shape-shifting Caused by Dark Matter

Abstract: Light sterile neutrinos with a mass of $\sim 1$ eV continue to be interesting due to multiple hints from terrestrial experiments. This simple hypothesis suffers from strong astrophysical constraints, in particular from the early universe as well as solar neutrinos. We develop a cosmologically viable proposal consistent with the terrestrial hints, as well as solar constraints, by sourcing the sterile neutrino's mass from ordinary matter via an ultralight scalar $\phi$ which can also be the dark matter. In this scenario, the experimentally implied $\sim 1$ eV sterile neutrino mass is a local value and changes throughout spacetime.