Single-step first order phase transition and gravitational waves in a SIMP dark matter scenario

Understand

We investigate the non-zero temperature dynamics of a sub-GeV dark matter scenario freezing-out via self-interactions.

• As a prototype, we take up the case of a scalar dark matter species undergoing $3 \to 2$ number changing annihilations catalysed by another scalar.
• We study the shape of the thermal potential of this scenario in a parameter region accounting for the observed relic abundance.
• An analysis reveals the possibility of a first order phase transition with bubble nucleation occurring at sub-GeV temperatures.