# Testing Seesaw and Leptogenesis with Gravitational Waves

## TL;DR

This paper explores how gravitational wave observations can test the seesaw mechanism and thermal leptogenesis, linking neutrino mass models with detectable cosmic string signals in future space missions.

## Contribution

It identifies symmetries that protect right-handed neutrinos and predicts gravitational wave signals from cosmic strings that can test leptogenesis models.

## Key findings

- Gravitational waves from cosmic strings could be detectable by future missions.
- Symmetries protecting neutrino masses can be tested through gravitational wave backgrounds.
- Future space missions can probe the entire parameter space relevant for thermal leptogenesis.

## Abstract

We present the possibility that the seesaw mechanism with thermal leptogenesis can be tested using the stochastic gravitational background. Achieving neutrino masses consistent with atmospheric and solar neutrino data, while avoiding non-perturbative couplings, requires right-neutrinos lighter than the typical scale of grand unification. This scale separation suggests a symmetry protecting the right handed neutrinos from getting a mass. Thermal leptogenesis would then require that such a symmetry be broken below the reheating temperature. We enumerate all such possible symmetries consistent with these minimal assumptions and their corresponding defects, finding that in many cases, gravitational waves from the network of cosmic strings should be detectable. Estimating the predicted gravitational wave background we find that future space-borne missions could probe the entire range relevant for thermal leptogenesis.