Executive Summary : | The presence of dark matter (DM) in the universe is still unknown, despite evidence from astrophysics and cosmology-based experiments. To accommodate this, several beyond standard model proposals have been proposed, including the weakly interacting massive particle (WIMP) paradigm. However, direct detection experiments have not found evidence of any WIMP DM particle for many years, leading to growing interest in alternative search strategies and non-WIMP DM candidates. This project aims to focus on cosmological and gravitational wave probes of both WIMP and non-WIMP type DM models. It will focus on models that can simultaneously explain non-zero neutrino mass and baryon asymmetry of the universe. The project will study the possibility of additional relativistic degrees of freedom (Neff), which can be observed up to unprecedented accuracy at future experiments like CMB-S4, SPT-3G. Neff can be changed due to the existence of additional light species or long-lived heavy particles decaying to photons or active neutrinos.
Regarding gravitational wave (GW) probes, the project will study the possibility of a strong first order phase transition (SFOPT) driven by DM or dark sector fields. In WIMP type models, the possibility of a strong electroweak phase transition or SFOPT around TeV scale will be studied, while in non-thermal or hidden sector DM models, sub-electroweak scale SFOPT will be explored. Topological defects like cosmic string and domain walls due to spontaneous symmetry breaking in DM and neutrino mass models with the resulting GW spectrum will also be studied. |