Speaker
Description
Gravitational Waves (GWs) offer a powerful window into the physics of the early Universe and could provide a novel probe of high-scale leptogenesis models. In this talk, I will explore how GW observations can shed light on a class of GUT-inspired seesaw models based on the $U(1)_{B-L}$ gauge symmetry. In these scenarios, the scalar field $\Phi$ responsible for the spontaneously breaking of $U(1)_{B-L}$ generates Majorana masses $M_N$ for right-handed neutrinos. Moreover, when the scalar field couples only feebly to the Standard Model Higgs, it naturally induces a period of early matter domination that is intimately connected to the leptogenesis scale $M_N$ and, therefore, encodes valuable information about different regimes of flavored leptogenesis. In this framework, GWs are produced both by the cosmic strings associated with the breaking of the gauge symmetry $U(1)_{B-L}$ and by the amplification of primordial density fluctuations during the early matter-dominated era. I will demonstrate how the amplitude and the spectral features of the resulting GW background are shaped by the underlying leptogenesis scale $M_N$. A future GW detection across multiple frequency bands could thus offer unique insights into the origin of the matter-antimatter asymmetry. Even in the absence of a signal, stringent constraints could be placed on the leptogenesis parameter space—constraints that are otherwise inaccessible through conventional probes.