Chilly dark sectors and asymmetric reheating

Research output: Contribution to journalArticle

Abstract

Abstract: In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, Neff , we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

Original languageEnglish (US)
Article number16
JournalJournal of High Energy Physics
Volume2016
Issue number6
DOIs
StatePublished - Jun 1 2016

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sectors
heating
asymmetry
universe
space temperature
cosmology
dark matter
histories
entropy
microwaves
collisions
temperature
radiation
scattering
interactions

Keywords

  • Cosmology of Theories beyond the SM
  • Thermal Field Theory

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

Chilly dark sectors and asymmetric reheating. / Adshead, Peter John; Cui, Yanou; Shelton, Julia F.

In: Journal of High Energy Physics, Vol. 2016, No. 6, 16, 01.06.2016.

Research output: Contribution to journalArticle

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