Abstract:
The early universe could feature multiple reheating events, leading to
jumps in the visible sector entropy density that dilute both particle
asymmetries and the number density of frozen-out states. In fact, late
time entropy jumps are usually required in models of Affleck-Dine
baryogenesis, which typically produces an initial
particle-antiparticle asymmetry that is much too large. An important
consequence of late time dilution, is that a smaller dark matter
annihilation cross section is needed to obtain the observed dark
matter relic density. For cosmologies with high scale baryogenesis,
followed by radiation-dominated dark matter freeze-out, the
perturbative unitarity mass bound on thermal relic dark matter is
relaxed to thousands of PeV. An extensive direct detection search
program is necessary to uncover such dark matter. Intriguingly, within
the dilute thermal relic framework, PeV mass asymmetric dark matter
could be responsible for the production of heavy r-process elements,
including gold. I will show how heavy asymmetric dark matter could be
found using the locations of neutron star mergers in galaxies, and by
observing a new type of astrophysical event, a “quiet kilonova.” In
addition, I will present recent progress on using thermal emission
from nearby pulsars to explore dark matter-nucleon scattering with a
precision that exceeds many planned direct detection experiments.