Gravitational waves from seesaw assisted collapsing domain walls

TL;DR

This paper explores how heavy right-handed neutrinos in the seesaw mechanism can generate bias terms that lead to collapsing domain walls, producing gravitational waves detectable by current and future experiments, and also relate to baryogenesis.

Contribution

It introduces a novel connection between seesaw neutrino physics, domain wall annihilation, gravitational wave signals, and baryon asymmetry, with potential experimental implications.

Findings

Heavy right-handed neutrinos generate bias terms via quantum corrections.

Correlation established between seesaw scale, GW peak amplitude, and frequency.

Tiny RHN couplings can explain baryon asymmetry through resonant leptogenesis.

Abstract

Spontaneous breaking of discrete symmetries like $Z_2$ leads to the formation of stable topological defects such as domain walls which, if allowed to dominate, can potentially be in conflict with cosmological observations. Incorporating explicit $Z_2$-breaking bias terms can lead to annihilation of such walls while also emitting stochastic gravitational wave (GW). We study the role of heavy right-handed neutrinos present in type-I seesaw origin of light neutrino masses to generate such bias term via quantum corrections. This offers interesting correlation among the seesaw scale, GW peak amplitude and peak frequency which can be probed at present and future experiments related to GW as well as precision measurements of the cosmic microwave background (CMB). In flavor symmetric UV complete scenarios with degenerate RHNs at leading order, such tiny coupling of RHNs to a $Z_2$-odd scalar can also lead to small mass splittings suitable for explaining the observed baryon asymmetry of the universe via resonant leptogenesis.