Dispersion of neutrinos in a medium

TL;DR

This paper investigates how neutrinos of different types disperse in a complex scalar medium, revealing unique dispersion relations that impact cosmological models and are constrained by astrophysical observations.

Contribution

It provides a perturbative analysis of neutrino dispersion relations in a scalar medium, highlighting differences between Majorana and Dirac neutrinos and implications for dark matter interactions.

Findings

Distinct dispersion relations for Majorana and Dirac neutrinos in non-relativistic limits

Medium-induced neutrino oscillations can occur under certain conditions

Constraints on model parameters from astrophysical neutrino observations

Abstract

We analyze the dispersion relations of Weyl or Majorana, and Dirac neutrinos in a complex scalar medium which interacts with the neutrinos through Yukawa couplings. They are solved by perturbative calculation in various limits representing different physical situations, some of which allow the medium-induced neutrino oscillation to occur. Remarkably, peculiar dispersion relations arise differently for Majorana or Dirac neutrinos in the non-relativistic limit. This provides an unpleasant restriction on the cosmological scenario of a scalar dark matter coupling to neutrinos. At present, the model parameter space is constrained by the neutrino scattering with dark matter through astrophysical neutrino observations.