Consists of lectures that are part of the MSRI workshops and that introduce students and researchers to the intriguing world of theoretical physics.This book consists of lectures that are part of the distinguished series of MSRI workshops and contains contributions by six different authors providing mathematics students and researchers with a bridge or a window into a portion of the intriguing world of theoretical physics, especially that which centers around Einstein gravitation and quantum field theory.This book consists of lectures that are part of the distinguished series of MSRI workshops and contains contributions by six different authors providing mathematics students and researchers with a bridge or a window into a portion of the intriguing world of theoretical physics, especially that which centers around Einstein gravitation and quantum field theory.This book provides an introduction to (1) various zeta functions (for example, Riemann, Hurwitz, Barnes, Epstein, Selberg, and Ruelle), including graph zeta functions; (2) modular forms (Eisenstein series, Hecke and Dirichlet L-functions, Ramanujan's tau function, and cusp forms); and (3) vertex operator algebras (correlation functions, quasimodular forms, modular invariance, rationality, and some current research topics including higher genus conformal field theory). Various concrete applications of the material to physics are presented. These include Kaluza-Klein extra dimensional gravity, Bosonic string calculations, an abstract Cardy formula for black hole entropy, Patterson-Selberg zeta function expression of one-loop quantum field and gravity partition functions, Casimir energy calculations, atomic Schr?dinger operators, Bose-Einstein condensation, heat kernel asymptotics, random matrices, quantum chaos, elliptic and theta function solutions of Einstein's equations, a soliton-black hole connection in two-dimensional gravity, and conformal field theory.Part I. Introductory Lectures: 1. Lectures on l3-