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14:00 Manibrata Sen (UC Berkeley and Northwestern University)
Title: The rise of keV sterile dark matter, again!
Abstract: Sterile neutrinos with masses around a few keV have been postulated to be viable dark matter candidates. This is, however, mostly in tension with various astrophysical observations, the most stringent being the X-ray bounds. In this talk, I would like to present a testable sterile neutrino dark matter production mechanism in the early universe. The idea is to introduce secret self-interactions among the Standard Model neutrinos. Such interactions can enable the sterile neutrinos to be more efficiently produced in the early universe, thus alleviating the tensions. These new interactions are usually stronger than the weak interactions, and hence can serve as a well-motivated target for the upcoming experimental searches.
14:30 Michael Waterbury (UC Irvine)
Title: Dark Matter Freeze Out during an Early Cosmological Period of QCD Confinement
Abstract: Standard lore states that there is tension between the need to accommodate the relic density of a weakly interacting massive particle and direct searches for dark matter. However, the estimation of the relic density rests on an extrapolation of the cosmology of the early Universe to the time of freeze out, untethered by observations. We explore a nonstandard cosmology in which the strong coupling constant evolves in the early Universe, triggering an early period of QCD confinement at the time of freeze out. We find that depending on the nature of the interactions between the dark matter and the Standard Model, freeze out during an early period of confinement can lead to drastically different expectations for the relic density, allowing for regions of parameter space which realize the correct abundance but would otherwise be excluded by direct searches.