RELATIVISTIC QUANTUM PHYSICS includes in its fold both Relativistic Quantum Mechanics and Quantum Field Theory. It is shown how Feynman's positron theory and Feynman diagrams have greatly simplified the calculations for various processes in Quantum Electrodynamics. Elements of Quantum Field Theory and its essential features are also presented. Neutrinos and neutrino oscillations, Gauge theories and Guage bosons, Higgs field and Higgs bosons, spontaneous symmetry breaking and Higgs mechanism, and how the particles acquire mass by Higgs mechanism are some of the topics that are dealt with exhaustively in this book.