Dark Matter from Exponential Growth
  We propose a novel mechanism for the production of dark matter (DM) from a
thermal bath, based on the idea that DM particles $\chi$ can transform heat
bath particles $\psi$: $\chi \psi \rightarrow \chi \chi$. For a small initial
abundance of $\chi$ this leads to an exponential growth of the DM number
density, in close analogy to other familiar exponential growth processes in
nature. We demonstrate that this mechanism complements freeze-in and freeze-out
production in a generic way, opening new parameter space to explain the
observed DM abundance, and we discuss observational prospects for such
scenarios.
