Naturally small neutrino mass with asymptotic safety and gravitational-wave signatures

TL;DR

This paper explores how asymptotic safety in quantum gravity can naturally generate small neutrino masses within the Standard Model and gauged B-L model, and discusses potential gravitational wave signatures from phase transitions.

Contribution

It demonstrates a mechanism for small neutrino masses via asymptotic safety, applicable to both Dirac and Majorana neutrinos, with potential gravitational wave detection signatures.

Findings

Neutrino masses can be generated naturally without extensions.

Gravitational wave signals from phase transitions are detectable but not distinctive.

The model aligns with quantum gravity calculations and accommodates various neutrino types.

Abstract

We revisit the dynamical generation of an arbitrarily small neutrino Yukawa coupling in the Standard Model with trans-Planckian asymptotic safety and apply the same mechanism to the gauged $B-L$ model. We show that thanks to the presence of additional irrelevant couplings, the described neutrino-mass generation in the $B-L$ model is potentially more in line with existing theoretical calculations in quantum gravity. Interestingly, the model can accommodate, in full naturalness and without extensions, the possibility of purely Dirac, pseudo-Dirac, and Majorana neutrinos with any see-saw scale. We investigate eventual distinctive signatures of these cases in the detection of gravitational waves from first-order phase transitions. We find that, while it is easy to produce a signal observable in new-generation interferometers, its discriminating features are washed out by the strong dependence of the gravitational-wave spectrum on the relevant parameters of the scalar potential.