The Quantum Theory of Radiation

4-vector absorption angle anticommutes approximation atom average Bremsstrahlung calculated charge classical theory collision commutation relations components Compton effect Compton scattering consider contribution Coulomb gauge cross-section denote depends effect emission emitted energy loss expectation value external field factor field strengths finite formula free electron free particles frequency given Hamiltonian high energies integration invariant joining points k₁ light quantum line breadth Lorentz condition Lorentz gauge magnetic magnetic moment mass matrix element momentum negative electron negative energy non-relativistic obtain occur operator order of magnitude oscillator pair creation photon Phys polarization positron primary Proc quanta quantization quantum electrodynamics quantum theory radiation field radiative corrections relativistic represents result satisfied scalar scattering second quantization second term self-energy subsection t₁ tensor test body tion transformation transition probability vacuum vanishes variables vector velocity virtual wave equation wave function zero