GR uniqueness and deformations
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In the metric formulation gravitons are described with the parity symmetric S + 2 ⊗ S − 2 representation of Lorentz group. General Relativity is then the unique theory of interacting gravitons with second order field equations. We show that if a chiral S + 3 ⊗ S − representation is used instead, the uniqueness is lost, and there is an infinite-parametric family of theories of interacting gravitons with second order field equations. We use the language of graviton scattering amplitudes, and show how the uniqueness of GR is avoided using simple dimensional analysis. The resulting distinct from GR gravity theories are all parity asymmetric, but share the GR MHV amplitudes. They have new all same helicity graviton scattering amplitudes at every graviton order. The amplitudes with at least one graviton of opposite helicity continue to be determinable by the BCFW recursion.
KeywordsScattering Amplitudes Classical Theories of Gravity
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- N. Arkani-Hamed, The amplituhedron, scattering amplitudes, and the wavefunction of the Universe, talk at New geometric structures in scattering amplitudes, September 22-25, Oxford U.K. (2014).