Effects of Neutrino-Ultralight Dark Matter Interaction on the Cosmic Neutrino Background

TL;DR

This paper explores how ultralight dark matter interacting with sterile neutrinos can alter the cosmic neutrino background's properties, affecting neutrino masses, mass ordering, and detection prospects in experiments like PTOLEMY.

Contribution

It introduces a model where neutrino-dark matter interactions induce redshift-dependent neutrino masses and can change neutrino mass ordering in the early universe.

Findings

Neutrino-dark matter interactions cause a redshift dependence in neutrino masses.

Such interactions can modify cosmological constraints on neutrino masses.

Alterations in neutrino mass ordering and detection rates are predicted.

Abstract

Ultralight dark matter interacting with sterile neutrinos would modify the evolution and properties of the cosmic neutrino background through active-sterile neutrino mixing. We investigate how such an interaction would induce a redshift dependence in neutrino masses. We highlight that cosmological constraints on the sum of neutrino masses would require reinterpretation due to the effective mass generated by neutrino-dark matter interactions. Furthermore, we present an example where such interactions can alter the mass ordering of neutrinos in the early Universe, compared to what we expect today. We also address the expected changes in the event rates in a PTOLEMY-like experiment, which aims to detect the cosmic neutrino background via neutrino capture, and discuss projected constraints.