Grid based linear neutrino perturbations in cosmological N-body simulations

We present a novel, fast and precise method for including the effect of light neutrinos in cosmological N-body simulations. The effect of the neutrino component is included by using the linear theory neutrino perturbations in the calculation of the gravitational potential in the N-body simulation. By comparing this new method with the full non-linear evolution first presented in [1], where the neutrino component was treated as particles, we find that the new method calculates the matter power spectrum with an accuracy better than 1% for Sigma m(v) less than or similar to 0.5eV at z = 0. This error scales approximately as(Sigma m(v))2,making the new linear neutrino method extremely accurate for a total neutrino mass in the range 0.05-0.3 eV. At z = 1 the error is below 0.3% for Sigma m(v) less than or similar to 0.5 eV and becomes negligible at higher redshifts. This new method is computationally much more efficient than representing the neutrino component by N-body particles.