From Cosmos to Colliders: Understanding Dark Matter

The nature of the dark matter sector of the Universe remains unknown, including the possibility that more than one particle species contributes to the observed dark matter abundance. In the first part of my talk, I will present a prescription for identifying thermal scenarios with two stable and distinct dark matter components at high-energy lepton colliders.

Such scenarios can lead to characteristic double peaks (or humps) in the missing energy or missing transverse momentum distributions of the final states. Depending on the underlying framework, these features may appear in multilepton or mono-X channels. In the second and third parts of the talk, I will discuss scenarios in which dark matter is produced nonthermally through BSM mediators.

In particular, I will explore the role of light BSM mediators and their implications for cosmological and astrophysical observations, focusing on constraints from the effective number of relativistic degrees of freedom, Neff, during CMB formation, as well as astrophysical probes such as Supernova (SN) 1987A.