Graviphoton
In theoretical physics, a graviphoton or gravivector is a hypothetical particle which emerges as an excitation of the metric tensor in spacetime dimensions higher than four, as described in Kaluza–Klein theory.
However, its crucial physical properties are analogous to a photon: it induces a "vector force", sometimes dubbed a "fifth force". The electromagnetic potential emerges from an extra component of the metric tensor, where the figure 5 labels an additional, fifth dimension.
In gravity theories with extended supersymmetry, a graviphoton is normally a superpartner of the graviton that behaves like a photon, and is prone to couple with gravitational strength, as was appreciated in the late 1970s. Unlike the graviton, however, it may provide a repulsive force, and thus, in some technical sense, a type of anti-gravity. Under special circumstances, then, in several natural models, often descending from five-dimensional theories mentioned, it may actually cancel the gravitational attraction in the static limit. Joël Scherk investigated semirealistic aspects of this phenomenon, stimutlating searches for physical manifestations of this mechanism.
