Dirac equation in the algebra of physical space Dirac equation in the algebra of physical space The Dirac equation, as the relativistic equation that describes spin 1/2 particles in quantum mechanics, can be written in terms of the Algebra of physical space (APS), which is a case of a Clifford algebra or geometric algebra that is based on the use of paravectors. The Dirac equation in APS, including the electromagnetic interaction, reads Another form of the Dirac equation in terms of the Space time algebra was given earlier by David Hestenes. In general, the Dirac equation in the formalism of geometric algebra has the advantage of providing a
Two-photon physics two-photon physics experiments can be used as ways to study the photon structure, or, somewhat metaphorically, what is "inside" the photon. There are three interaction processes: For the latter two cases, the scale of the interaction is such as the strong coupling constant is large. This is called "Vector Meson Dominance" (VMD) and has to be modelled in non-perturbative QCD. Two-photon physics Two-photon physics, also called gamma–gamma physics, is a branch of particle physics that describes the interactions between two photons. Normally, beams of light pass through each other unperturbed. Inside an optical material, and if the intensity of the