Illustration: Courtesy of Shankar Agarwal and Hume Feldman, University of Kansas; submitted to Mon. Not. R. Astron. Soc.
Comparison of density distribution in the Universe with (left) and without (right) massive neutrinos. The maps are based on numerical simulations . The colors account for the density of ordinary (baryonic) matter in one slice of the simulation box . The two simulations started from the same initial conditions, with either (right) or (left). In the massive neutrino case, matter is spread over a larger number of structures and there is less density contrast. (The unrealistically large neutrino mass of was chosen so as to make the comparison clear.)