Variations on the Vev Flip-Flop: Instantaneous Freeze-out and Decaying Dark Matter

Understand

In this work we consider a simple model for dark matter and identify regions of parameter space where the relic abundance is set via kinematic thresholds, which open and close due to thermal effects.

• We discuss instantaneous freeze-out, where dark matter suddenly freezes-out when the channel connecting dark matter to the thermal bath closes, and decaying dark matter, where dark matter freezes-out while relativistic and later decays when a kinematic threshold temporarily opens.
• These mechanisms can occur in the vicinity of a one-step or a two-step phase transition.
• In all cases thermal effects provide this dynamic behaviour, while ensuring that dark matter remains stable until the present day.