Probing cosmology using dark matter microhalos
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 microhalos hinders their usage as cosmological probes. A theoretical understanding of the microhalo-cosmology connection demands numerical simulation, but microhalos are too small and dense to simulate up to the present day in full cosmological context. My research meets this challenge by using controlled numerical simulations to develop (semi)analytic models of dark matter structure. I will discuss these models, which describe the formation of the first halos and their subsequent evolution as they accrete onto larger systems. I will also explore two applications: 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.