What we can learn from atmospheric neutrinos

Physics potential of future measurements of atmospheric neutrinos is explored. Observation of $\Delta m^2_{21}$ driven sub-dominant effects and $\theta_{13}$ driven large matter effects in atmospheric neutrinos can be used to study the deviation of $\theta_{23}$ from maximality and its octant. Neutrino mass hierarchy can be determined extremely well due to the large matter effects. New physics can be constrained both in standard atmospheric neutrino experiments as well as in future neutrino telescopes.