Advanced Quantum Theory and Its Applications Through Feynman Diagrams

Book excerpt: The fundamental goal of physics is an understanding of the forces of nature in their simplest and most general terms. Yet the scientific method inadver tently steers us away from that course by requiring an ever finer subdivision of the problem into constituent components, so that the overall objective is often obscured, even to the experts. The situation is most frustrating and acute for today's graduate students, who must try to absorb as much general knowledge as is possible and also try to digest only a sm all fraction of the ever increasing morass of observational data or detailed theories to write a dissertation. This book is based on the premise that to study a subject in depth is only half the battle; the remaining struggle is to put the pieces together in a broad but comprehensive manner. Accordingly, the primary purpose of this text is to cut across the barriers existing between the various fields ofmodern physics (elementary particles; nuclear, atomic, and solid state physics; gravitation) and present a unified description of the quantum nature of forces encountered in each field at the level of the second-year physics graduate student. This unification is based on one-body perturbation techniques, covariantly generalized to what are now called "Feynman diagrams," and is formulated aS,a simple (but nontriv ial) extension of ordinary nonrelativistic, one-particle quantum theory.