the relativistic velocity vector; the four-velocity vector; the square of the length of the four-velocity vector; the four-momentum vector; the relativistic energy of a particle; the relativistic expression for the kinetic energy; the energy-momentum four-vector; the energy-momentum relation; the relativistic relation between the energy and momentum for a particle with zero mass; conservation of energy and momentum; Compton scattering; relativisitic electron-positron collision experiments; relativistic description of the decay of a particle; The Dirac theory of the electron; the probability current; the continuity equation; the Klein-Gordon equation; the Dirac equation; the Dirac matrices; the Dirac-Pauli representation of the Dirac matrices; the Pauli spin matrices the covariant form of the Dirac equation; plane wave solutions of the Dirac equation; the positive and negative solutions of the Dirac equation; Dirac’s description of the negative energy states; anti-particles states; field quantization; Feynman diagrams; quantum field theory