SQG2 - Loop Quantum Gravity, Quantum Geometry, Spin Foams |
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Speaker |
Bahr, Benjamin |
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Talk Title |
Perfect actions in Regge calculus |
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Abstract |
In discretizing reparametrization invariant theories, the reparametrization invariance is generically lost. This is usually due to a failure of discrete energy conservation. A similar situation occurs in discretizing GR along the lines of Regge Calculus, which unlike GR in general exhibits unique solutions for given boundary data. In this talk it is argued that, to capture the diffeomorphism symmetry of GR correctly, one should try to restore the reparametrization invariance by considering so-called perfect actions, which are also used in the context of lattice QCD. These are actions formulated on a discrete lattice or triangulation, but reproduce the continuum dynamics of the theory. We show how to construct perfect actions for Regge calculus in general, and derive the perfect action in 3D with cosmological constant. |
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