Date: 
September 9, 2008, 15:30  16:30 
Place: 
Seminar Room at IPMU Prefab. B, Kashiwa Campus of the University of Tokyo 
Speaker: 
Mitsuru Kakizaki (Bonn University) 
Title: 
Abundance of Thermal Relics in Nonstandard Cosmological Scenarios

Abstract: 
We investigate the relic density of nonrelativistic longlived or
stable particles in nonstandard cosmological scenarios. We derive
approximate solution for the relic density which accurately reproduce
numerical results when full thermal equilibrium is not achieved.
Assuming that thermally produced WIMPs account for the observed dark
matter energy density, we obtain the lower bound on the reheat
temperature, and constrain possible modifications of the Hubble
expansion rate. We also propose a new ansatz for the
thermallyaveraged annihilation cross section of relic particles that
decouple semirelativistically, and derive an approximate analytic
solution for their abundance. Some applications of such
semirelativistically decoupled relics are discussed
