Self-heating of Strongly Interacting Massive Particles

Understand

It was recently pointed out that semi-annihilating dark matter (DM) may experience a novel temperature evolution dubbed as self-heating.

• Exothermic semi-annihilation converts the DM mass to the kinetic energy.
• This yields a unique DM temperature evolution, $T_{\chi} \propto 1 / a$, in contrast to $ T_{\chi} \propto 1 / a^{2}$ for free-streaming non-relativistic particles.
• Self-heating continues as long as self-scattering sufficiently redistributes the energy of DM particles.