2007/04/30 by Manuel Drees, Hoernisa Iminniyaz, M. Kakizaki +1 · 2 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Particle physics theoretical and experimental studies #astro-ph #hep-ph
paper · pdf · doi:10.1103/physrevd.76.103524
published as Phys.Rev.D76:103524,2007 · 23 pages, 8 figures, comments added
openalex publication_date 2007/11/15 · arxiv created 2007/11/16 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We investigate the relic density n_\ensuremathχ of nonrelativistic long-lived or stable particles \ensuremathχ in nonstandard 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 T0\ensuremath≥m_\ensuremathχ/23, assuming that thermally produced \ensuremathχ particles account for the dark matter energy density in the Universe; this bound holds for all \ensuremathχ 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 \ensuremathχ 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\ensuremath∼m_\ensuremathχ/20, well before big bang nucleosynthesis.