Lattice diffeomorphism invariance
Abstract
We propose a lattice counterpart of diffeomorphism symmetry in the continuum. A functional integral for quantum gravity is regularized on a discrete set of spacetime points, with fermionic or bosonic lattice fields. When the spacetime points are positioned as discrete points of a continuous manifold, the lattice action can be reformulated in terms of average fields within local cells and lattice derivatives. Lattice diffeomorphism invariance is realized if the action is independent of the positioning of the spacetime points. Regular as well as rather irregular lattices are then described by the same action. Lattice diffeomorphism invariance implies that the continuum limit and the quantum effective action are invariant under general coordinate transformations—the basic ingredient for general relativity. In our approach the lattice diffeomorphism invariant actions are formulated without introducing a metric or other geometrical objects as fundamental degrees of freedom. The metric rather arises as the expectation value of a suitable collective field. As examples, we present lattice diffeomorphism invariant actions for a bosonic nonlinear sigma model and lattice spinor gravity.
 Publication:

Physical Review D
 Pub Date:
 May 2012
 DOI:
 10.1103/PhysRevD.85.104017
 arXiv:
 arXiv:1110.1539
 Bibcode:
 2012PhRvD..85j4017W
 Keywords:

 04.20.Gz;
 04.60.Kz;
 11.15.Ha;
 Spacetime topology causal structure spinor structure;
 Lower dimensional models;
 minisuperspace models;
 Lattice gauge theory;
 High Energy Physics  Lattice;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 More detailed proof of diffeomorphism symmetry of quantum effective action, 17 pages