VSI Seminar, Rouzbeh Allahverdi
Early Matter Domination from Long-Lived Particles in the Visible Sector
Nonstandard cosmological histories with epochs of early matter domination have attracted significant attention recently. I argue that a sub-TeV particle in the visible sector can drive a period of early matter domination rather naturally. This scenario involves a long-lived neutral particle that acquires a thermal abundance from decays and inverse decays of a parent particle with standard model charges, and subsequently dominates the energy density of the universe. Entropy generation at the end of early matter domination dilutes the abundance of dangerous relics (such as gravitinos) by a factor as large as 10^4. The scenario can accommodate the correct dark matter relic abundance for both cases with small and large annihilation rates. More importantly, the allowed parameter space can be directly probed by proposed searches for neutral long-lived particles at the energy frontier, allowing us to use particle physics experiments to reconstruct the cosmological history just prior to big bang nucleosynthesis.