Matteo Viel: Cosmology with Massive Neutrinos
(I apologize for the incomplete writeup of this presentation; I still publish it due to the importance of the claimed limit on the sum of neutrino masses below – TD)
At the start the speaker showed an extra-cool 3D simulation of the universe including neutrinos. the videos are available at http://som.ific.uv.es (e.g. here); in them you can see a large cube encompassing large-scale structures of dark matter in the universe, and the associated more diffuse concentration of neutrinos.
The sum of masses of 3 neutrinos is presently constrained to lie between 0.056 and 6 eV. Neutrinos can be treated as a fluid with a thermal velocity in the universe. They cannot form structures and they delay structure formation. The larger the neutrino mass, the larger is the suppression of cluster formation.
A non-linear simulation the suppression of smaller structures is larger by 20%. We want to consider the neutrino halo around dark matter. It is more diffuse and we can characterize its properties, plotting the density profile which has a shape depending on the total neutrino mass. If you want to know how much overdensity is due to neutrino in the halo of the milky way, depending on the neutrino mass you have significant fractions.
A Bayesian analysis employing 1-D Lyman-alpha flux power, including CMB and baryonic acoustic oscillation data returns a sum of neutrino masses lower than 0.14 eV at 95% confidence level.