What Dark Matter Microhalos Can Tell us About Reheating

          @misc{ pirsa_PIRSA:11090082,
            doi = {10.48660/11090082},
            url = {https://pirsa.org/11090082},
            author = {Erickcek, Adrienne},
            keywords = {Particle Physics},
            language = {en},
            title = {What Dark Matter Microhalos Can Tell us About Reheating},
            publisher = {Perimeter Institute},
            year = {2011},
            month = {sep},
            note = {PIRSA:11090082 see, \url{https://pirsa.org}}
          }
          

Abstract

The expansion history of the Universe before big bang nucleosynthesis is unknown; in many models, the Universe was effectively matter-dominated between the end of inflation and the onset of radiation domination. I will show how an early matter-dominated era leaves an imprint on the small-scale matter power spectrum. This imprint depends on the origin of dark matter. If dark matter originates from the radiation bath after reheating, then small-scale density perturbations are suppressed, leading to a cut-off in the matter power spectrum. Conversely, small-scale density perturbations are significantly enhanced if the dark matter was created nonthermally during reheating. These enhanced perturbations trigger the formation of numerous dark matter microhalos during the cosmic dark ages. The abundance of dark matter microhalos is therefore a new window on the Universe before nucleosynthesis.