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
Non-physical entity a ghost that makes it a specifically non-physical, rather than a physical entity. Were the existence of ghosts ever demonstrated beyond doubt, it has been claimed that would actually place them in the category of "physical" entities. Purported non-mental non-physical entities include things such as gods, angels, demons, and ghosts. Lacking demonstrations of their existence, their existences and natures are widely debated, independently of the philosophy of mind. Non-physical entity In ontology and the philosophy of mind, a non-physical entity is a spirit or being that exists outside physical reality. Their existence divides the philosophical school of physicalism from the