Neutrinos, ultra-high-energy cosmic rays and fundamental physics

Aspects of neutrino physics beyond the Standard Model are emphasized, including the emerging default options for atmospheric and solar neutrino oscillations, namely nu /sub mu / to nu /sub tau / and nu /sub e/ to nu /sub mu , tau / respectively, and the need to check them, the prospects opened up by the successful starts of SNO and K2K and the opportunities for future long-baseline neutrino experiments. The author then discusses how cosmic rays may provide opportunities for probing fundamental physics. For example, ultra-high-energy cosmic rays might originate from the decays of metastable heavy particles, and astrophysical gamma -rays can be used to test models of quantum gravity. Both scenarios offer ways to avoid the GZK cut- off, and might best be probed using high-energy astrophysical neutrinos. (89 refs).