Thermal Resummation, Dark Matter, and Baryogenesis: Higgs-Portal Windows into the Early Universe with Subhojit Roy

The nature of the electroweak phase transition can provide crucial hints of new physics beyond the Standard Model (BSM). If the transition is first order, it can support electroweak baryogenesis (EWBG) and generate stochastic gravitational waves within reach of upcoming detectors. An accurate description of the scalar potential at finite temperature is therefore essential for studying cosmological first-order phase transitions. At high temperatures, bosonic fields suffer from infrared divergences that can spoil ordinary perturbation theory, making thermal resummation techniques indispensable for reliable predictions. I will discuss how different thermal resummation schemes, including tadpole resummation, impact the dynamics of first-order transitions, illustrating these effects within the two-Higgs-doublet model, which serves as a popular BSM Higgs-extension case study. In the latter part of the talk, I will present a dark matter framework--the inelastic Higgs-portal scenario--which remains compatible with the latest direct-detection limits, can explain the long-standing Galactic-Center gamma-ray excess, and realizes a strong first-order transition. In this setup, a CP-violating dimension-6 operator enables EWBG, linking the dark matter relic abundance, baryon asymmetry, and gravitational-wave signatures within a unified Higgs-portal framework.

This lecture was made possible by the William C. Ferguson Fund.