Quantum field theory

Professor Susskind introduces quantum field theory.  Excepting gravity, quantum field theory is our most complete description of the universe.  Each quantum field corresponds to a specific particle type, and is represented by a state vector consisting of the number of particles in each possible energy state.  These numbers are called occupation numbers.  This representation uses the same quantum mathematics as a state vector for multiple harmonic oscillators with the basis vectors being the energy state of each oscillator.  Therefore the quantum field mathematics follow those introduced for harmonic oscillators in previous lectures.  However, in the case of quantum field theory, the raising and lowering operators become operators which create and destroy particles in a given energy state.