Constraints on Dark Matter interactions from structure formation: damping lengths

By Céline Boehm, R. Schaeffer. 2004

153 citations recorded by the source corpus.

Weakly Interacting Massive Particles are often said to be the best Dark Matter candidates. Studies have shown that large Dark Matter-photon or Dark Matter-baryon interactions could be allowed by cosmology. Here we address the question of the role of the Dark Matter interactions in more detail to determine at which extent Dark Matter has to be necessarily weakly interacting. To this purpose, we compute the collisional damping (and free-streaming) scales of generic interacting Dark Matter candidates and investigate the effects on structure formation. Our calculations are valid provided the Dark Matter particles have experienced a phase of statistical equilibrium at some stage during their evolution. By comparing these damping lengths to the scale of the smallest primordial structures known to exist in the Universe, we obtain necessary conditions that any candidate must satisfy. These conditions are expressed in terms of the Dark Matter particles' mass and either the total Dark Matter interaction rate or the interaction rate of Dark Matter with a specific species. The case of Dark Matter interacting with neutrinos or photons is considered in full detail. Our results are valid even for energy dependent cross-sections and for any possible initial fluctuations spectrum. We point out the existence of new Dark Matter scenarios and exhibit new damping regimes. For example, an interacting candidate may bear a similar damping than that of collisionless Warm Dark Matter particles. The main difference is due to the Dark Matter coupling to interacting (or even freely-propagating) species. Our approach yields a general classification of Dark Matter candidates which extends the definitions of the usual Cold, Warm and Hot Dark Matter scenarios when interactions, weak or strong, are considered.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/05f899f1b7738605a4e32db5890ce957600e7f96

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Citations in the corpus

Dark matter halo merger histories beyond cold dark matter – I. Methods and application to warm dark matter (2012, background): “Several extensions to dark matter phenomenology (Markevitch et al. 2004; Ahn & Shapiro 2005; Boehm & Schaeffer 2005; Miranda & Macciò 2007; Randall et al. 2008; Boyarsky et al. 2009; Lovell et al. 2012) E-mail: abenson@obs.carnegiescience.edu and several different particle physics candidates for…”
Constraints on Dark Matter Microphysics from the Milky Way Satellite Population (2019, unknown): “2 Note that Boehm et al. (2001); Boehm & Schaeffer (2005) perform similar derivations for DM–photon and DM–neutrino scattering models. where zcrit is the corresponding redshift.”
Using the Milky Way satellites to study interactions between cold dark matter and radiation (2014, background): “2 We use the Newtonian gauge, where the Thomson scattering terms are omitted for brevity. fluids (Boehm et al. 2001; Boehm & Schaeffer 2005) leading to a damping scale l2cd,γ ∼ ∫ tdec(DM−γ) 0 ργ c 2 ρ Γγ a2 dt , (3) where ργ is the photon energy density, ρ is total energy density, Γγ is the total…”
Reducing the H0 and σ8 tensions with dark matter-neutrino interactions. (2017, background): “Dark matter-baryon and dark matter self-interactions can also erase the DM fluctuations but the u ratio needs to be of order 1 to produce the same effects as the one considered here [2,3], given that there are many less baryons than radiation in the Universe and baryons are nonrelativistic.”
The 511 keV emission from positron annihilation in the Galaxy (2010, background): “…down to the MeV range) may then account for the observed dark 22 The mixed damping effect is in fact analogous to the ”Silk damping”, with dark matter playing the role of baryons and neutrinos replacing the photons (Boehm et al., 2001; Boehm and Schaeffer, 2005). matter relic density in that case.”