Speaker
Dr
Mitsuru Kakizaki
(Physics Institute, Bonn University)
Description
We investigate the relic density n_\chi of non-relativistic long-lived or stable
particles \chi in non-standard cosmological scenarios. We calculate the relic
abundance starting from arbitrary initial temperatures of the radiation-
dominated epoch, and derive the lower bound on the initial temperature T_0
\geq m_\chi/23, assuming that thermally produced \chi particles account for the
dark matter energy density in the universe; this bound holds for all \chi
annihilation cross sections. We also investigate cosmological scenarios with
modified expansion rate. Even in this case an approximate formula similar to the
standard one is capable of predicting the final relic abundance correctly.
Choosing the \chi annihilation cross section such that the observed cold dark
matter abundance is reproduced in standard cosmology, we constrain possible
modifications of the expansion rate at T \sim m_\chi/20, well before Big Bang
nucleosynthesis.
Author
Dr
Mitsuru Kakizaki
(Physics Institute, Bonn University)
Co-authors
Dr
Hoernisa Iminniyaz
(Physics Institute, Bonn University)
Prof.
Manuel Drees
(Physics Institute, Bonn University)
