Bounds on Neutrino Mass in Viscous Cosmology

Understand

Effective field theory of dark matter fluid on large scales predicts the presence of viscosity of the order of $10^{-6} H_0 M_P^2$.

• It has been shown that this magnitude of viscosities can resolve the discordance between large scale structure observations and Planck CMB data in the $\sigma_8$-$\Omega_m^0$ and $H_0$-$\Omega_m^0$ parameters space.
• Massive neutrinos suppresses the matter power spectrum on the small length scales similar to the viscosities.
• We show that by including the effective viscosity, which arises from summing over non linear perturbations at small length scales, severely constrains the cosmological bound on neutrino masses.