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GR: Fachverband Gravitation und Relativitätstheorie

GR 1: Kosmologie

GR 1.5: Vortrag

Montag, 3. März 2008, 18:05–18:25, KGI-HS 1010

Warm dark matter with a non-zero chemical potential — •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

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 (Ω_Λ⁰ = 0.72, Ω_M⁰ = 0.28, 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 1.8 eV ≤ m ≤ 53 eV, where the upper bound scales linearly with g_eff^s(T_Dec). From LSS we find that similar to ordinary warm dark matter models the particle mass has to be larger than ∼ 500 eV (meaning g_eff^s(T_Dec) > 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.