2+1 gravity on the conformal sphere

  title={2+1 gravity on the conformal sphere},
  author={Sean Gryb and Flavio Mercati},
  journal={Physical Review D},
We show that there are two equivalent first order descriptions of $2+1$ gravity with a nonzero cosmological constant. One is the well-known spacetime description, and the other is in terms of evolving conformal geometry. The key tool that links these pictures is Cartan geometry, a generalization of Riemannian geometry that allows for geometries locally modeled off arbitrary homogeneous spaces. The two different interpretations suggest two distinct phase space reductions. The spacetime picture… 

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