Composite gravity

Class of models of gravitation treating gravitons as composite particles

In theoretical physics, composite gravity refers to models that attempted to derive general relativity in a framework where the graviton is constructed as a composite bound state of more elementary particles, usually fermions. A theorem by Steven Weinberg and Edward Witten shows that this is not possible in Lorentz covariant theories: massless particles with spin greater than one are forbidden. The AdS/CFT correspondence may be viewed as a loophole in their argument. However, in this case not only the graviton is emergent; a whole spacetime dimension is emergent, too.^[1]

References

^ Okui, Takemichi (2006). "Probing composite gravity in colliders". Physical Review D. 73 (7). scitation.aip.org: 075012. arXiv:hep-ph/0511082. Bibcode:2006PhRvD..73g5012O. doi:10.1103/PhysRevD.73.075012. S2CID 34102365. Retrieved 2008-07-08.

Theories of gravitation

Standard

Newtonian gravity (NG)	Newton's law of universal gravitation Gauss's law for gravity Poisson's equation for gravity History of gravitational theory
General relativity (GR)	Introduction History Mathematics Exact solutions Resources Tests Post-Newtonian formalism Linearized gravity ADM formalism Gibbons–Hawking–York boundary term

Alternatives to
general relativity

Paradigms	Classical theories of gravitation Quantum gravity Theory of everything
Classical	Poincaré gauge theory Einstein–Cartan Teleparallelism Bimetric theories Gauge theory gravity Composite gravity f(R) gravity Infinite derivative gravity Massive gravity Modified Newtonian dynamics, MOND AQUAL Tensor–vector–scalar Nonsymmetric gravitation Scalar–tensor theories Brans–Dicke Scalar–tensor–vector Conformal gravity Scalar theories Nordström Whitehead Geometrodynamics Induced gravity Degenerate Higher-Order Scalar-Tensor theories
Quantum-mechanical	Euclidean quantum gravity Canonical quantum gravity Wheeler–DeWitt equation Loop quantum gravity Spin foam Causal dynamical triangulation Asymptotic safety in quantum gravity Causal sets DGP model Rainbow gravity theory
Unified-field-theoric	Kaluza–Klein theory Supergravity
Unified-field-theoric and quantum-mechanical	Noncommutative geometry Semiclassical gravity Superfluid vacuum theory Logarithmic BEC vacuum String theory M-theory F-theory Heterotic string theory Type I string theory Type 0 string theory Bosonic string theory Type II string theory Little string theory Twistor theory Twistor string theory
Generalisations / extensions of GR	Liouville gravity Lovelock theory (2+1)-dimensional topological gravity Gauss–Bonnet gravity Jackiw–Teitelboim gravity