Discrete gravity as a topological field theory with lightlike curvature defects
Abstract
I present a model of discrete gravity as a topological field theory with defects. The theory has no local degrees of freedom and the gravitational field is trivial everywhere except at a number of intersecting null surfaces. At these null surfaces, the gravitational field can be singular, representing a curvature defect propagating at the speed of light. The underlying action is local and it is studied in both its Lagrangian and Hamiltonian formulation. The canonically conjugate variables on the null surfaces are a spinor and a spinorvalued twosurface density, which are coupled to a topological field theory for the Lorentz connection in the bulk. I discuss the relevance of the model for nonperturbative approaches to quantum gravity, such as loop quantum gravity, where similar variables have recently appeared as well.
 Publication:

Journal of High Energy Physics
 Pub Date:
 May 2017
 DOI:
 10.1007/JHEP05(2017)142
 arXiv:
 arXiv:1611.02784
 Bibcode:
 2017JHEP...05..142W
 Keywords:

 Lattice Models of Gravity;
 Models of Quantum Gravity;
 Topological Field Theories;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Lattice;
 High Energy Physics  Theory;
 Mathematical Physics
 EPrint:
 52 pages, one figure, one table, v2: published version with extended conclusion