Prospects for the direct detection of the cosmic neutrino background
  The existence of a cosmic neutrino background -- the analogue of the cosmic
microwave background -- is a fundamental prediction of standard big bang
cosmology. Up to now, the observational evidence for its existence is rather
indirect and rests entirely on cosmological observations of, e.g., the light
elemental abundances, the anisotropies in the cosmic microwave background, and
the large scale distribution of matter. Here, we review more direct, weak
interaction based detection techniques for the cosmic neutrino background in
the present epoch and in our local neighbourhood. We show that, with current
technology, all proposals are still off by some orders of magnitude in
sensitivity to lead to a guaranteed detection of the relic neutrinos. The most
promising laboratory search, based on neutrino capture on beta decaying nuclei,
may be done in future experiments designed to measure the neutrino mass through
decay kinematics.
