Evolution of the phase-space density and the Jeans scale for dark matter derived from the Vlasov-Einstein equation

Abstract

We discuss solutions of Vlasov-Einstein equation for collisionless dark matter particles in the context of a flat Friedmann universe. We show that, after decoupling from the primordial plasma, the dark matter phase-space density indicator Q remains constant during the expansion of the universe, prior to structure formation. This well known result is valid for non-relativistic particles and is not "observer dependent" as in solutions derived from the Vlasov-Poisson system. In the linear regime, the inclusion of velocity dispersion effects permits to define a physical Jeans length for collisionless matter as function of the primordial phase-space density indicator: λ_J = (5π/G)^(1/2)Q^(-1/3)ρ_dm^(-1/6). The comoving Jeans wavenumber at matter-radiation equality is smaller by a factor of 2-3 than the comoving wavenumber due to free-streaming, contributing to the cut-off of the density fluctuation power spectrum at the lowest scales. We discuss the physical differences between these two scales. For dark matter particles of mass equal to 200 GeV, the derived Jeans mass is 4.3 x 10^(-6) solar masses.

18 pages, 2 figures. Accepted for publication in JCAP

References in corpus (9)

• First Dark Matter Results from the XENON100 Experiment
• Strong constraints on the rare decays Bs -> mu+ mu- and B0 -> mu+ mu-
• Constraints on dark matter particles from theory, galaxy observations and N-body simulations
• Toward A Consistent Picture For CRESST, CoGeNT and DAMA
• Constrained Supersymmetry after two years of LHC data: a global view with Fittino
• Dark Matter Accretion into Supermassive Black Holes
• Hamiltonian Dynamics of Spatially-Homogeneous Vlasov-Einstein Systems
• Evidence for dark matter modulation in CoGeNT?
• Gravitational collapse in an expanding background and the role of substructure I: Planar collapse

Cited by in corpus (7)

• New Constraints on the Mass of Fermionic Dark Matter from Dwarf Spheroidal Galaxies
• Is the continuous matter creation cosmology an alternative to $\Lambda$CDM?
• Cannibal domination and the matter power spectrum
• Dark matter velocity dispersion effects on CMB and matter power spectra
• Cannibalism's lingering imprint on the matter power spectrum
• Evolution of dark matter velocity dispersion
• General relativistic non-ideal fluid equations for dark matter from a truncated cumulant expansion