Reducing the H₀ and σ₈ tensions with dark matter-neutrino interactions

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 H₀ and a slight decrease of S₈≡σ₈√{Ω_m/0.3 } , which can help reduce somewhat the tension between the CMB and weak lensing or Cepheids data sets. Here we show that it is impossible to solve both tensions simultaneously. While the 2015 Planck temperature and low multipole polarization data combined with the Cepheids data sets prefer large values of the Hubble rate (up to H₀=72.1_-1.7^+1.5 km /s /Mpc , when N_eff is free to vary), the σ₈ parameter remains too large to reduce the σ₈ tension. Adding high multipole Planck polarization data does not help since this data shows a strong preference for low values of H₀, thus worsening current tensions, even though they also prefer smaller value of σ₈.