How to Detect Big Bang Relic Neutrinos?
  The existence of big bang relic neutrinos - exact analogues of the big bang relic photons comprising the cosmic microwave background radiation - is a basic prediction of standard cosmology. At present, the observational evidence for their existence rests entirely on cosmological measurements, such as the light elemental abundances, anisotropies in the cosmic microwave background, and the large-scale matter power spectrum. In this review, we concentrate on the prospects of more direct, weak interaction based relic neutrino detection techniques which are sensitive to the cosmic neutrino background near the present epoch and in our local neighborhood in the universe. In this connection, we emphasize the necessity to take into account the gravitational clustering of the relic neutrinos in the cold dark matter halos of our Milky Way and nearby galaxy clusters. 
Andreas Ringwald (DESY)