Light sterile neutrinos from a late phase transition

TL;DR

This paper proposes a new class of models where light sterile neutrinos are compatible with cosmological data due to a late phase transition in a hidden sector, avoiding previous tensions.

Contribution

It introduces scenarios with late phase transitions in hidden sectors that allow multiple light sterile neutrinos without conflicting with cosmological observations.

Findings

Identifies parameter regions with multiple sterile neutrinos compatible with data

Shows late phase transition can prevent topological defect issues

Demonstrates models are robust against cosmological constraints

Abstract

Light sterile neutrinos represent a well-motivated extension of the 3-neutrino paradigm. However, the impressive agreement between standard cosmology and data casts doubts on their existence. Here we present a class of scenarios that robustly avoids this tension. In these models the sterile neutrinos are light, chiral states of a new sector interacting with the Standard Model via the right-handed neutrino portal and, crucially, active-sterile neutrino oscillations require a phase transition in the hidden sector. We explore the hidden-couplings/critical-temperature plane and identify regions where several sterile neutrinos can be accommodated. A late phase transition is usually preferred and may also ward off a potential threat posed by the formation of topologically stable defects.