Latest Cosmological Constraints on the Densities of Hot and Cold Dark Matter

As experimentalists step up their pursuit of cold dark matter particles and neutrino masses, cosmological constraints are tightening. We compute the joint constraints on 11 cosmological parameters from cosmic microwave background and large scale structure data, and find that at 95\% confidence, the total (cold+hot) dark matter density is h2$\Omega$dm = 0.20+.12−.10 with at most 38\% of it being hot (due to neutrinos). A few assumptions, including negligible neutrinos, tighten this measurement to h2$\Omega$dm = 0.13+0.04−0.02, i, e., 2.4 \texttimes 10−27kg/m3 give or take 20\%.