Results from Super-Kamiokande on atmospheric neutrino and limits on matter instability

Latest atmospheric neutrino results from 1489 days exposure of the Super-Kamiokande detector are presented. Our data are well explained by two flavor v(mu) <----> v(tau) oscillations. In the three flavor oscillation case, the result shows no evidence for non zero theta(13). Other models, v(tau) - v(s) admixture and neutrino decay, are strongly constrained. Moreover, the appearance searches for tau neutrino interactions are performed. Our data are consistent with v(tau) appearance. For the nucleon decay, p --> e(+)pi(0) and p --> (v) over barK(+) are searched for, but no evidence for nucleon decays has been found. Experimental lower limits for nucleon partial lifetime are obtained to be 5.7 x 10(33) years for p - e(+)pi(0) and 2.0 x 1033 years for p -->(v) over barK(+).