An accurate fluid approximation for massive neutrinos in cosmology

Understand

A measurement of the neutrino mass scale will be achieved with cosmological probes in the upcoming decade.

• On one hand, the inclusion of massive neutrinos in the linear perturbation theory of cosmological structure formation is well understood and can be done accurately with state of the art Boltzmann solvers.
• On the other hand, the numerical implementation of the Boltzmann equation is computationally expensive and is a bottleneck in those codes.
• This has motivated the development of more efficient fluid approximations, despite their limited accuracy over all scales of interest, $k \sim (10^{-3}-10)$Mpc$^{-1}$.