Reducing the $H_0$ and $\sigma_8$ tensions with Dark Matter-neutrino interactions

TL;DR

This paper investigates Dark Matter-neutrino interactions as a potential solution to the H_0 and σ_8 tensions in cosmology, finding that while they can slightly alleviate these tensions, they cannot resolve both simultaneously.

Contribution

It demonstrates that Dark Matter-neutrino interactions cannot fully solve the H_0 and σ_8 tensions, especially when considering different Planck polarization datasets.

Findings

Dark Matter-neutrino interactions slightly increase H_0

They slightly decrease σ_8

Simultaneous resolution of both tensions is not possible

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 $\sigma_8$, 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 $\sigma_8$ parameter remains too large to reduce the $\sigma_8$ 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 $\sigma_8$.