Many-Body Theory (or Many-body physics) is an area of physics which provides the framework for understanding the collective behavior of vast assemblies of interacting particles. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. In general terms, the many-body theory deals with effects that manifest themselves only in systems containing large numbers of constituents.
See also many-body problem. The many-body problem may be defined as the study of the effects of interaction between bodies on the behaviour of a many-body system i