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arXiv · 1904.11906

Bi-gravity with a single graviton

Sergei Alexandrov·Simone Speziale
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Abstract

We analyze a bi-gravity model based on the first order formalism, having as fundamental variables two tetrads but only one Lorentz connection. We show that on a large class of backgrounds its linearization agrees with general relativity. At the non-linear level, additional degrees of freedom appear, and we reveal the mechanism hiding them around the special backgrounds. We further argue that they do not contain a massive graviton, nor the Boulware-Deser ghost. The model thus propagates only one graviton, whereas the nature of the additional degrees of freedom remains to be investigated. We also present a foliation-preserving deformation of the model, which keeps all symmetries except time diffeomorphisms and has three degrees of freedom.

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Sergei Alexandrov, Simone Speziale. 2019-04-26. Bi-gravity with a single graviton. https://doi.org/10.1007/jhep08(2019)070

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