Pheno & Vino Seminar, Jakub Scholtz, Harvard, "Flooded Dark Matter and core/cusp resolution with fermionic dark matter"

Feb 23, 2016, 4:00 pm5:30 pm
Jadwin 303


Event Description
Most dark matter (DM) models set the DM relic density by some interaction with Standard Model particles. Such models generally assume the existence of Standard Model particles early on, with the DM relic density a later consequence of those interactions. Perhaps a more compelling assumption is that DM is not part of the Standard Model sector and a population of DM too is generated at the end of inflation. This democratic assumption does not necessarily provide a natural value for the DM relic density, and superficially leads to too much entropy in the dark sector. We address the latter issue by the late decay of heavy particles produced at early times, associating the DM relic density with the lifetime of a long-lived state. We ask what it would take for this scenario to be compatible with observations in what we call Flooded Dark Matter (FDM) and discuss several interesting consequences. One is that DM can be very light and furthermore, light DM is in some sense the most natural scenario in FDM as it is compatible with larger couplings of the decaying particle. Moreover, the decay of the field with the smallest coupling and hence the longest lifetime dominates the entropy and possibly the matter content of the Universe, a principle we refer to as 'Maximum Baroqueness'. We also show that the dark sector should be colder than the ordinary sector, relaxing the free-streaming constraints on light DM and I will discuss the implications for the core-cusp problem.