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Reducing the $H_0$ and $σ_8$ tensions with Dark Matter-neutrino interactions

Eleonora Di Valentino, Céline Bøehm, Eric Hivon, François R. Bouchet

TL;DR

This paper investigates dark matter–neutrino (DM–ν) interactions as a modification to LCDM to address the H_0 and σ_8 tensions inferred from CMB observations. By solving the DM–ν–modified Boltzmann equations and performing Bayesian analyses with Planck 2015 data across multiple dataset combinations (including polarization, lensing, and an R16 H_0 prior), the authors quantify the impact on H_0, σ_8, and N_eff, Σm_ν. They find that while DM–ν interactions can raise H_0 and lower σ_8, they cannot resolve both tensions simultaneously, especially when high-ℓ polarization data are included, though the tensions can be modestly alleviated under certain assumptions or parameter freedoms. The results place robust upper bounds on the interaction strength and suggest that any potential resolution may hinge on new physics such as dark radiation, with DESI/Euclid offering critical tests.

Abstract

The introduction of Dark Matter-neutrino interactions modifies the Cosmic Microwave Background (CMB) angular power spectrum at all scales, thus affecting the reconstruction of the cosmological parameters. Such interactions can lead to a slight increase of the value of $H_0$ and a slight decrease of $σ_8$, which can help reduce somewhat the tension between the CMB and lensing or Cepheids datasets. Here we show that it is impossible to solve both tensions simultaneously. While the 2015 Planck temperature and low multipole polarisation data combined with the Cepheids datasets prefer large values of the Hubble rate (up to $H_0 = 72.1^{+1.5}_{-1.7} \rm{km/s/Mpc}$, when $N_{\rm{eff}}$ is free to vary), the $σ_8$ parameter remains too large to reduce the $σ_8$ tension. Adding high multipole Planck polarization data does not help since this data shows a strong preference for low values of $H_0$, thus worsening current tensions, even though they also prefer smaller value of $σ_8$.

Reducing the $H_0$ and $σ_8$ tensions with Dark Matter-neutrino interactions

TL;DR

This paper investigates dark matter–neutrino (DM–ν) interactions as a modification to LCDM to address the H_0 and σ_8 tensions inferred from CMB observations. By solving the DM–ν–modified Boltzmann equations and performing Bayesian analyses with Planck 2015 data across multiple dataset combinations (including polarization, lensing, and an R16 H_0 prior), the authors quantify the impact on H_0, σ_8, and N_eff, Σm_ν. They find that while DM–ν interactions can raise H_0 and lower σ_8, they cannot resolve both tensions simultaneously, especially when high-ℓ polarization data are included, though the tensions can be modestly alleviated under certain assumptions or parameter freedoms. The results place robust upper bounds on the interaction strength and suggest that any potential resolution may hinge on new physics such as dark radiation, with DESI/Euclid offering critical tests.

Abstract

The introduction of Dark Matter-neutrino interactions modifies the Cosmic Microwave Background (CMB) angular power spectrum at all scales, thus affecting the reconstruction of the cosmological parameters. Such interactions can lead to a slight increase of the value of and a slight decrease of , which can help reduce somewhat the tension between the CMB and lensing or Cepheids datasets. Here we show that it is impossible to solve both tensions simultaneously. While the 2015 Planck temperature and low multipole polarisation data combined with the Cepheids datasets prefer large values of the Hubble rate (up to , when is free to vary), the parameter remains too large to reduce the tension. Adding high multipole Planck polarization data does not help since this data shows a strong preference for low values of , thus worsening current tensions, even though they also prefer smaller value of .

Paper Structure

This paper contains 7 sections, 1 equation, 3 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Impact of the DM-$\nu$ interactions on the cosmological parameters
  3. Method
  4. Results based on the "Planck TT + lowTEB" datasets only
  5. Results with the polarization data
  6. Results with R16
  7. Conclusion

Figures (3)

  • Figure 1: The temperature and polarization CMB angular power spectra in the presence of Dark Matter-neutrino interactions.
  • Figure 2: Triangle plot showing the 1D and 2D posterior distributions of the cosmological parameters for Planck TT + lowTEB in the $\Lambda$CDM + $u$ + $N_{\mathrm{eff}}$ scenario.
  • Figure 3: Triangle plot showing the 1D and 2D posterior distributions of the cosmological parameters for Planck TTTEEE + lowTEB in the $\Lambda$CDM + $u$ scenario.