Small-scale power spectrum of cold dark matter

By Abraham Loeb, M. Zaldarriaga. 2005

193 citations recorded by the source corpus.

One of the best motivated hypotheses in cosmology states that most of the matter in the universe is in the form of weakly-interacting massive particles that decoupled early in the history of the universe and cooled adiabatically to an extremely low temperature. Nevertheless, the finite temperature and horizon scales at which these particles decoupled imprint generic signatures on their small-scale density fluctuations. We show that the previously recognized cut-off in the fluctuation power-spectrum due to free-streaming of particles at the thermal speed of decoupling, is supplemented by acoustic oscillations owing to the initial coupling between the cold dark matter (CDM) and the radiation field. The power-spectrum oscillations appear on the scale of the horizon at kinematic decoupling which corresponds to a mass scale of {approx}10{sup -4}(T{sub d}/10 MeV){sup -3}M{sub {center_dot}} for a CDM decoupling temperature T{sub d}. The suppression of the power-spectrum on smaller scales by the acoustic oscillations is physically independent from the free-streaming effect, although the two cut-off scales are coincidentally comparable for T{sub d}{approx}10 MeV and a particle mass of M{approx}100 GeV. The initial conditions for recent numerical simulations of the earliest and smallest objects to have formed in the universe, need to be modified accordingly. Themore » smallest dark-matter clumps may be detectable through {gamma}-ray production from particle annihilation, through fluctuations in the event rate of direct detection experiments, or through their tidal gravitational effect on wide orbits of objects near the outer edge of the solar system.« less

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/d8c6b694e5f7872a66de9dd63c86e532dc066ada

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

Characterization of subhalo structural properties and implications for dark matter annihilation signals (2016, background): “The minimum halo mass depends on the free-streaming of DM particles from high to low density regions (Zybin et al. 1999; Hofmann et al. 2001; Berezinsky et al. 2003; Green et al. 2005) and on the effect of acoustic oscillations (Loeb & Zaldarriaga 2005; Bertschinger 2006).”
Axion dark matter, solitons and the cusp–core problem (2015, background): “The freestreaming and decoupling lengths of a WIMP and the Jeans scale of the QCD axion are both extremely small (i.e. subsolar on a mass scale; see e.g. Loeb & Zaldarriaga 2005).”
The Dark Matter Annihilation Signal from Galactic Substructure: Predictions for GLAST (2008, background): “In principle this hierarchy could extend all the way down to the cut-off in the matter power spectrum, set by collisional damping and free streaming in the early universe (Green et al. 2005; Loeb & Zaldarriaga 2005).”
Non-Abelian dark matter and dark radiation (2015, result): “This is in contrast with the more frequently studied case where the DM interactions freeze out at a critical temperature, leading to a sharp cutoff in the power spectrum at small scales [3, 21–23].”
SEARCH FOR DARK MATTER SATELLITES USING FERMI-LAT (2012, unknown): “…the resolution to recover all satellites down to a mass of "-' 10 6 1\1(,), the minimum mass of a bound satellite orbiting the Milky Way may be as low as the Earth mass ("-' 10-6 1\1(,)), a scale that is roughly set by the WIMP velocity at freeze-out (Hofmann et al. 2001; Loeb & Zaldarriaga 2005).”
ETHOS - an effective theory of structure formation: dark matter physics as a possible explanation of the small-scale CDM problems (2015, result): “(7) This result for the evolved, non-linear power spectrum agrees to within about a factor of 2 with earlier analytic estimates for this regime (Loeb & Zaldarriaga 2005; Bertschinger 2006; Bringmann 2009), based on definitions ofMcut related to the form of the linear power spectrum.”
Hidden charged dark matter (2009, methodology): “[52, 54]: the oscillation amplitude is much smaller than it is in the WIMP case.”
Dark matter halo merger histories beyond cold dark matter – I. Methods and application to warm dark matter (2012, background): “In practice, this is not true as even CDM will have some cutoff in its power spectrum on very small scales (Green, Hofmann & Schwarz 2004; Loeb & Zaldarriaga 2005).”
The first WIMPy halos (2005, methodology): “In order to compare our analytic results with the numerical result of [18], we express the cut-off scales in terms of matter mass enclosed in a sphere of radius R = π/kfs, Mcut(R) ≈ 4.”
Galactic Searches for Dark Matter (2012, background): “For standard cold dark matter particles with mass around the weak scale and freeze-out temperatures & GeV, the minimum mass subhalo is predicted to be somewhere in the range of an Earth mass (Green et al., 2004; Loeb and Zaldarriaga, 2005; Profumo et al., 2006; Martinez et al., 2009).”