Cosmological neutrino bounds for non-cosmologists Tegmark 2 Department of Physics, Univers ity of Pennsylvania, Philadelphia, PA 19104, USA (Dated: February 18, 2004. To appear in Neutrino Physics, proceedings of the Nobel Symposium 2004) (Enkoping, Sweden, August 19-24, 2004, Eds. L. Bergstrom, O. Botner, P. Carlson, P.O. Hulth T Ohlsson) I briefly review cosmological bounds on neutrino masses and the underlying gravitational physics t a level appropriate for readers outside the field of cosmology. For the case of three massive neutrinos with standard model freezeout, the current 95% upper limit on the sum of their masses is 0.42 eV. I summarize the basic physical mechanism making matter clustering such a sensitive probe of massive neutrinos. I discuss the prospects of doing still better in coming years using tools such as lensing tomography, approaching a sensitivity around 0.03 eV. Since the lower bound from detect neutrino mass if the technical and fiscal challenges can be met ogical measurements should atmospheric neutrino oscillations is around 0.05 eV, upcoming cosmo Wavelengthλ[h-lMpc] 104 1000 z104 0.8 000 60.6 O SDSS galaxies ☆ Cluster abundance 0.2 ▲ Lyman Alpha Forest 0.5 0.001 0.01 Wavenumber k [h/Mpc 0.1 0.15 0.2 Dark matter density wdhep-ph/0503257