Co-genesis in the Early Universe: Connecting Dark Matter and Baryon Asymmetry via FOPT

by Indrajit Saha (IIT Guwahati)

Thursday 28 Aug 2025, 16:00 → 17:30 Asia/Seoul

Room 1423 (KIAS)

Title: Co-genesis in the Early Universe: Connecting Dark Matter and Baryon Asymmetry via FOPT

Speaker:  Indrajit Saha (IIT Guwahati)

Abstract: In this talk, I will explore a class of scenarios where finite-temperature effects near a first-order phase transition (FOPT) open up novel pathways for the simultaneous generation of baryon asymmetry and dark matter abundance, a phenomenon we term \textit{co-genesis}. At high temperatures, thermal masses can transiently enable decay channels that are forbidden at zero temperature, providing a natural setting for baryogenesis or leptogenesis without violating the late-time stability of dark matter. I will illustrate this mechanism within minimal extensions of the Standard Model, such as the scotogenic model, which includes an additional scalar doublet and right-handed neutrinos stabilised by a (Z2) symmetry. In such frameworks, the lightest right-handed neutrino, stable at zero temperature, can decay within a finite thermal window into leptons and inert scalars, generating a lepton asymmetry that is subsequently converted into a baryon asymmetry via sphaleron processes. These thermal co-genesis mechanisms are closely linked to gravitational wave signals originating from the associated FOPTs, providing a rare opportunity to correlate dark matter, baryogenesis, and neutrino cosmology with upcoming gravitational wave experiments such as LISA and (\mu)ARES.