Speaker
Description
We preset the linear cosmological evolution of inelastic self-interacting dark matter in a two-component dark sector with a small mass splitting, assuming thermal initial conditions for the two species.
We derive the coupled background and perturbation equations for inelastic conversion between the two species,
considering both power-law and velocity-saturated cross sections.
Exothermic conversion injects kinetic energy into the light component, generating pressure support that suppresses small-scale structure and produces dark acoustic oscillations in the matter power spectrum.
The resulting cutoff at scale $k>1$~Mpc/$h$ depends on the velocity dependence of the cross section,
the mass splitting, and the dark matter mass.
Using linear power spectra computed with a modified Boltzmann solver,
we apply recast constraints from Lyman-$\alpha$ forest data and high-redshift UV luminosity functions,
finding non-monotonic but closed exclusion regions driven by the competition between efficient conversion and rapid depletion of the heavy component.
These results show that the internal thermodynamics of a secluded multi-component dark sector can leave observable imprints on structure formation, providing a complementary probe of dark matter beyond Standard Model interactions.
