Combinatorics and physics Combinatorics and physics Combinatorial physics or physical combinatorics is the area of interaction between physics and combinatorics. "Combinatorial Physics is an emerging area which unites combinatorial and discrete mathematical techniques applied to theoretical physics, especially Quantum Theory.". "Physical combinatorics might be defined naively as combinatorics guided by ideas or insights from physics". Combinatorics has always played an important role in quantum field theory and statistical physics. However, combinatorial physics only emerged as a specific field after a seminal work by Alain Connes and Dirk Kreimer, showing that the renormalization of Feynman diagrams can be described by a Hopf algebra. Combinatorial
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