This volume contains discussions on group representations of SL(2,R) and automorphic forms, with applications of the Selberg trace formula to the Landau spectrum for a uniform magnetic field on a Riemann surface, on particle creation in the early universe, Chern-Simons gauge theory on 3-manifolds, path integral representation of fractional spin particles, eta and zeta functions and Dirac operators, Schrödinger operators with periodic potential, elliptic genera for SUSY sigma models, quantum fields on curved space-times, black holes, and some discussions on string theory and quantum gravity.