UNC-CH Physics and Astronomy PhD Defense

Sten Delos

“Probing the Early Universe Using Dark Matter Minihalos”

Through their observable properties, the first and smallest dark matter halos represent a rare probe of subkiloparsec-scale variations in the density of the early Universe. These density variations could hold clues to the nature of inflation, the postinflationary cosmic history, and the identity of dark matter. However, the dynamical complexity of these minihalos hinders their usage as cosmological probes. A theoretical understanding of the minihalo-cosmology connection demands numerical simulation, but minihalos are too small and dense to simulate up to the present day in full cosmological context. This dissertation meets this challenge by using controlled numerical simulations to develop (semi)analytic models of dark matter structure. These models describe the formation of the first halos and their subsequent evolution as they accrete onto larger systems, both through tidal forces and encounters with other objects. I also explore two observational applications of the minihalo-cosmology connection: breaking a degeneracy between the properties of thermal-relic dark matter and the postinflationary history, and probing inflation’s late stages via the small-scale primordial power spectrum.

This defense will be held remotely through Zoom. Please see department listservs for more details.