Neutrino Masses from Outer Space

TL;DR

This paper proposes a model where neutrino masses evolve over cosmological timescales due to coupling with an ultralight field, linking neutrino physics with cosmology and quantum gravity considerations.

Contribution

It introduces a natural, dynamic mechanism for neutrino mass generation via an ultralight field, connecting particle physics, cosmology, and quantum gravity conjectures.

Findings

Neutrino masses can vary over cosmic time scales.

Mass variation affects sterile neutrino populations.

The framework offers potential observational tests related to quantum gravity.

Abstract

Neutrinos can gain mass from coupling to an ultralight field in slow roll. When such a field is displaced from its minimum, its vev acts just like the Higgs vev in spontaneous symmetry breaking. Although these masses may eventually vanish, they do it over a very long time. The theory is technically natural, with the ultralight field-dependent part being the right-handed Majorana mass. The mass variation induced by the field correlates with the cosmological evolution. The change of the mass term changes the mixing matrix, and therefore suppresses the fraction of sterile neutrinos at earlier times and increases it at later times. Since the issue of quantum gravity corrections to field theories with large field variations remains open, this framework may give an observational handle on the Weak Gravity Conjecture.