Discrete quantum gravity: applications to cosmology

TL;DR

This paper applies a consistent lattice quantum gravity approach to cosmological models, exploring the removal of singularities, the continuum limit, and the introduction of relational time in quantum cosmology.

Contribution

It extends the lattice quantum gravity framework to cosmology, analyzing discretizations, symmetries, and the emergence of continuum behavior, and introduces a relational time concept.

Findings

Removal of Big Bang singularity demonstrated

Continuum limit analyzed in various models

Relational time introduced in quantum cosmology

Abstract

We consider the application of the consistent lattice quantum gravity approach we introduced recently to the situation of a Friedmann cosmology and also to Bianchi cosmological models. This allows us to work out in detail the computations involved in the determination of the Lagrange multipliers that impose consistency, and the implications of this determination. It also allows us to study the removal of the Big Bang singularity. Different discretizations can be achieved depending on the version of the classical theory chosen as a starting point and their relationships studied. We analyze in some detail how the continuum limit arises in various models. In particular we notice how remnants of the symmetries of the continuum theory are embodied in constants of the motion of the consistent discrete theory. The unconstrained nature of the discrete theory allows the consistent introduction of a relational time in quantum cosmology, free from the usual conceptual problems.