Place: 241 Nicholson
Date: Wednesday November 16th
Time: 11am
Title: Discrete Gravity as a topological field theory with defects
Abstract:
I give a proposal for discrete GR (as a field theory) in terms of self-dual variables. The manifold is spilt into four-dimensional regions, which are flat or constantly curved inside. The boundary of every such four-cell is a three-surface, which is taken to be null. The contribution to the action from the four-cells is trivial, only the internal three-boundaries and two-dimensional corners contribute non-trivially. Finding the right dynamics boils then down to finding the right boundary term. On a null surface, the natural such boundary term is built from a spinor and a spinor-valued two-form, which are canonically conjugate to each other. I discuss the relevance of the model for non-perturbative approaches to quantum gravity, such as loop quantum gravity, where similar variables have recently appeared as well. The talk is based on the paper: arXiv:1611.02784
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