Cosmology of fermionic dark matter

Tillmann Boeckel and Jürgen Schaffner-Bielich
Phys. Rev. D 76, 103509 – Published 5 November 2007

Abstract

We explore a model for a fermionic dark matter particle family which decouples from the rest of the particles when at least all standard model particles are in equilibrium. We calculate the allowed ranges for mass and chemical potential to be compatible with big bang nucleosynthesis (BBN) calculations and WMAP data for a flat universe with dark energy (ΩΛ0=0.72, ΩM0=0.27, h=0.7). Futhermore we estimate the free streaming length for fermions and antifermions to allow comparison to large scale structure data (LSS). We find that for dark matter decoupling when all standard model particles are present even the least restrictive combined BBN calculation and WMAP results allow us to constrain the initial dark matter chemical potential to a highest value of 6.3 times the dark matter temperature. In this case, the resulting mass range is at most 1.8eVm53eV, where the upper bound scales linearly with geffs(TDec). From LSS we find that, similar to ordinary warm dark matter models, the particle mass has to be larger than 500eV [meaning geffs(TDec)>103] to be compatible with observations of the Ly α forest at high redshift, but still the dark matter chemical potential over temperature ratio can exceed unity.

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  • Received 24 July 2007

DOI:https://doi.org/10.1103/PhysRevD.76.103509

©2007 American Physical Society

Authors & Affiliations

Tillmann Boeckel and Jürgen Schaffner-Bielich

  • Institut für Theoretische Physik/Astrophysik, J. W. Goethe Universität, Max-von-Laue-Straße 1, D-60438 Frankfurt am Main, Germany

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Issue

Vol. 76, Iss. 10 — 15 November 2007

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