Interaction of neutrinos with a cosmological k-essence scalar

Abstract

In this paper we study a novel means of coupling neutrinos to a Lorentz violating background k-essence field. We first look into the effect that k-essence has on the neutrino dispersion relation and derive a general formula for the neutrino velocity in the presence of a k-essence background. The influence of k-essence coupling on neutrino oscillations is then considered. It is found that if k-essence couples non-diagonally to the neutrino flavor eigenstates, then this leads to an oscillation length that goes like λ ∼ E −1, where E is the neutrino energy. This should be contrasted with the λ ∼ E dependence seen in mass-induced neutrino oscillations. While such a scenario is not favored experimentally, it places constraints on the possible interaction that a k-essence background can have with neutrinos by requiring it to be flavor diagonal. All nontrivial physical effects discussed here require the sound speed of k-essence fluctuations to be different from the speed of light, and hence are primarily a consequence of Lorentz violation.