Cosmological bounds on dark matter-neutrino interactions

TL;DR

The paper investigates cosmological bounds on neutrino–dark-matter interactions for MeV-scale dark matter by parameterizing the cross section with two regimes, $\langle \sigma_{dm-\nu}|v| \rangle \propto a^{-2}$ and a constant case, and introducing opacities $Q_2$ and $Q_0$. It analyzes linear perturbations with modified Euler equations, predicting diffusion-damped oscillations in the dark-matter density field, and constrains these effects using SDSS galaxy clustering data. The authors compare cosmological constraints with astrophysical bounds from SN1987A, finding $Q_2 \lesssim 10^{-42}\ \mathrm{cm^2\,MeV^{-1}}$ and $Q_0 \lesssim 10^{-34}\ \mathrm{cm^2\,MeV^{-1}}$, with stronger SN bounds on $Q_2$ in some regimes and the possibility that only a DM fraction couples, which relaxes limits. They argue that a relic-density–consistent scenario requires a DM particle–antiparticle asymmetry and that detection of NIDM-induced oscillations would imply such an asymmetry, providing a concrete target for future CMB+LSS analyses. The work narrows viable DM–neutrino interaction parameter space and links potential small-scale structure signatures to fundamental dark-sector asymmetries.

Abstract

We investigate the cosmological effects of a neutrino interaction with cold dark matter. We postulate a neutrino that interacts with a ``neutrino interacting dark matter'' (NIDM) particle with an elastic-scattering cross section that either decreases with temperature as $T^2$ or remains constant with temperature. The neutrino--dark-matter interaction results in a neutrino--dark-matter fluid with pressure, and this pressure results in diffusion-damped oscillations in the matter power spectrum, analogous to the acoustic oscillations in the baryon-photon fluid. We discuss the bounds from the Sloan Digital Sky Survey on the NIDM opacity (ratio of cross section to NIDM-particle mass) and compare with the constraint from observation of neutrinos from supernova 1987A. If only a fraction of the dark matter interacts with neutrinos, then NIDM oscillations may affect current cosmological constraints from measurements of galaxy clustering. We discuss how detection of NIDM oscillations would suggest a particle-antiparticle asymmetry in the dark-matter sector.

Figures (6)

• Figure 1: Dark-matter perturbations of $k=1.04\,h\,$Mpc$^{-1}$; the opacity $Q_{2}$ is in unit of cm$^{2}$ MeV$^{-1}$. Damped oscillations are clearly seen for $Q_2=10^{-39}$ cm$^{2}$ MeV$^{-1}$.
• Figure 2: Several matter power spectra with different opacities $Q_{2}$ (top panel) and $Q_0$ (bottom panel) between dark matter and neutrinos; $Q_{2}$ and $Q_0$ are in units of cm$^{2}$ MeV$^{-1}$.
• Figure 3: Angular power spectra with and without dark-matter--neutrino coupling. A small enhancement ($\sim 10\%$) of the height of the peaks on small scales is observed.
• Figure 4: Matter power spectra for cold+interacting dark matter with $Q_{2}=10^{-38}$cm$^{2}$ MeV$^{-1}$ (top panel) and $Q_2=10^{-37}$cm$^{2}$ MeV$^{-1}$ (bottom panel).
• Figure 5: Constraints on the $Q_2$ vs $\Omega_{NIDM}$ plane from SDSS $P(k)$ measurements. An overall matter density of $\Omega_m=0.27$ is assumed with $\Omega_b=0.04$.