Cold+Hot Dark Matter Cosmology withm(νμ)≈m(ντ)≈2.4eV

Cold $+$ hot dark matter (CHDM) $\Omega =1\mathrm{}$ cosmological models require a total neutrino mass $\sim 5$ eV. Because recent data support the ${\nu }_{\mu }\to {\nu }_{\tau }$ oscillation explanation of the cosmic ray ${\nu }_{\mu }$ deficit, which requires that $m\left({\nu }_{\mu }\right)\approx m\left({\nu }_{\tau }\right)$, this suggests that $m\left({\nu }_{\mu }\right)\approx m\left({\nu }_{\tau }\right)\approx 2.4$ eV. The linear calculations and $N$-body simulation reported here indicate that an $\Omega =1\mathrm{}$ CHDM model with two 2.4 eV neutrinos (designated $\mathrm{C}{\nu }^2$DM) agrees remarkably well with all available observations, but only if the Hubble parameter $h\approx 0.5$. We also show that even one 2.4 eV neutrino raises serious difficulties for low- $\Omega$ flat CDM models.