Low-Scale Leptogenesis and the Domain Wall Problem in Models with Discrete Flavor Symmetries

TL;DR

This paper introduces a leptogenesis mechanism in models with discrete flavor symmetries, where temperature-dependent symmetry breaking and domain wall dynamics enable lepton asymmetry generation at accessible energy scales.

Contribution

It presents a novel leptogenesis scenario leveraging discrete flavor symmetries and domain wall evolution, linking symmetry breaking to neutrino mass generation and baryogenesis.

Findings

Leptogenesis can occur at temperatures below gravitino bounds.

Domain walls are eliminated during the QCD phase transition due to the anomaly.

Symmetry breaking controls Majorana neutrino masses in the model.

Abstract

We propose a new mechanism for leptogenesis, which is naturally realized in some models with a flavor symmetry based on the discrete group A_4, where the symmetry breaking parameter also controls the Majorana masses for the heavy right handed (RH) neutrinos. During the early universe, for T>TeV, part of the symmetry is restored, due to finite temperature contributions, and the RH neutrinos remain massless and can be produced in thermal equilibrium even at temperatures well below the most conservative gravitino bounds. Below this temperature the phase transition occurs and they become massive, decaying out of equilibrium and producing the necessary lepton asymmetry. Unless the symmetry is broken explicitly by Planck-suppressed terms, the domain walls generated by the symmetry breaking survive till the quark-hadron phase transition, where they disappear due to a small energy splitting between different vacua caused by the QCD anomaly.