Dark Matter: Evidence and Candidates

This lecture focuses on the topic of dark matter, beginning with a recap of previous discussions on baryogenesis and the thermal history of the universe. The instructor transitions to dark matter, emphasizing the evidence for its existence and the various candidates proposed to explain it. The lecture outlines the significant role dark matter plays in cosmology, noting that while its existence is well-supported by observational data, its exact nature remains unknown. The instructor discusses the historical observations that led to the recognition of dark matter, including rotation curves of stars in galaxies and gravitational lensing effects. The lecture also covers the theoretical implications of dark matter, including its properties such as being stable and weakly interacting. Various candidates for dark matter are explored, including neutrinos, axions, and WIMPs, along with their respective challenges and constraints. The discussion concludes with the potential for dark matter to consist of primordial black holes, highlighting the ongoing research and exploration in this field.