Dark Matter, Shared Asymmetries, and Galactic Gamma Ray Signals
  We introduce a novel dark matter scenario where the visible sector and the
dark sector share a common asymmetry. The two sectors are connected through an
unstable mediator with baryon number one, allowing the standard model baryon
asymmetry to be shared with dark matter via semi-annihilation. The present-day
abundance of dark matter is then set by thermal freeze-out of this
semi-annihilation process, yielding an asymmetric version of the WIMP miracle
as well as promising signals for indirect detection experiments. As a proof of
concept, we find a viable region of parameter space consistent with the
observed Fermi excess of GeV gamma rays from the galactic center.
