Gravitational Discovery for Particle Physics

Since Lemaıtre and Hubble, a century of observations of the expansion history and structure of the universe has used gravity as a tool for discovery, establishing that the vast majority of matter and energy in the universe cannot be explained within the Standard Model and requires particle physics Beyond the Standard Model (BSM). Nearly all current efforts to determine the nature of dark matter explore hypothetical non-gravitational interactions between Standard Model particles and dark particles. However, if dark matter consists of more than one type of particle, the most important interactions for cosmology, and perhaps for dark matter discovery, might take place within the dark sector.

To understand the full potential of gravitational discovery for BSM physics, this focus initiative will pursue the following: How can we characterize the space of complex dark sectors, focusing on parts of parameter space with novel observational signatures? What are the key aspects of structure formation on small scales in scenarios where dark matter is complex, and dissipative? How can observations from gravitational waves, microlensing, and weak lensing probes of the small-scale structure of dark matter best be used to constrain or discover new physics?