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 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 schools of idealism and dualism; with the latter schools holding that they can exist and the former holding that they cannot. If one posits that non-physical entities can exist, there exist further debates as to their inherent natures and their position relative to physical entities. Philosophers generally do agree on the existence of abstract objects. These include concepts such as numbers, mathematical sets and functions, and philosophical relations