Leptogenesis via Bubble Collisions

TL;DR

This paper proposes a new leptogenesis mechanism where sterile neutrinos produced from bubble collisions during a first order phase transition generate the universe's matter-antimatter asymmetry, with detectable gravitational wave signals.

Contribution

It introduces a novel leptogenesis scenario from bubble collisions that allows high-scale RHN production without high reheat temperatures, extending viability to RHN masses above 10^{14} GeV.

Findings

Enables leptogenesis at RHN masses > 10^{14} GeV.

Predicts gravitational wave signals from phase transitions.

Suppresses washout effects in leptogenesis.

Abstract

We present a novel realization of leptogenesis from the decays of sterile (right-handed) neutrinos (RHNs) produced from runaway bubble collisions at a first order phase transition. Such configurations can produce heavy RHNs with mass many orders of magnitude above the scale of symmetry breaking as well as the temperature of the plasma, thereby enabling high scale leptogenesis without the need for high reheat temperatures while also naturally suppressing washout effects. This mechanism also extends the window of viability to RHN masses $\gtrsim 10^{14}$ GeV, the natural scale for type-I seesaw with $\mathcal{O}(1)$ couplings, where standard thermal leptogenesis cannot produce the observed baryon asymmetry. The corresponding phase transitions are at scales $\gtrsim\!10^9$ GeV and produce gravitational wave signals that could be detected by future experiments.