Neutrino mass and cosmic flows

Neutrinos are established to be massive and the mass differences have been measured, but the absolute neutrino mass values remain unknown. Cosmic neutrinos with finite mass slightly suppress the matter power spectrum below their free-streaming scale and this effect can be applied to constrain neutrino masses. However, the challenge of this method is to disentangle the complex and poorly understood baryonic effects and to obtain better optical depth measurements from the cosmic microwave background experiments. In this talk, I will discuss the effects of the relative velocity between dark matter and neutrino fluids and how to use them to constrain neutrino masses with nonlinear reconstruction methods. The new method is not affected by most systematics which are parity even and not limited by the knowledge of optical depth to the cosmic microwave background, rendering it a new promising probe of neutrino properties.