Conformally Invariant Brans-Dicke Loop Quantum Cosmology: A Quantum Geometric Model of Linking Theory

TL;DR

This paper develops a loop quantum cosmology model for conformal Brans-Dicke theory, integrating quantum geometric features and linking it with shape dynamics, revealing a unified quantum geometric framework.

Contribution

It introduces a loop quantization of conformal Brans-Dicke cosmology, connecting it with shape dynamics through a shared physical Hilbert space and conformal symmetry.

Findings

Derived Schrödinger evolutions with relational observables.

Unified loop quantum cosmology of GR and shape dynamics.

Established an exact dictionary linking the two theories.

Abstract

The loop quantization of the conformal Brans-Dicke cosmology is explored in the spatially flat and Bianchi-I setting. The scalar and conformal constraints governing the canonical model are quantized using the loop techniques. The physical Hilbert space of quantum spacetimes satisfying both quantum constraints is then obtained by incorporating the quantum geometric features. The Schr\"odinger cosmic evolutions are derived with the relational Heisenberg observables describing the dynamical degrees of freedom with respect to the chosen reference degrees of freedom, with the latter providing the physical coordinates for the spatial hypersurfaces and the conformal scales. We show that the emerging Schr\"odinger theories contain not only the loop quantum cosmology of GR, but also that of the so-called shape dynamics. The exact dictionary between the two theories is achieved via the underlying physical Hilbert space possessing the additional (loop-corrected) conformal symmetry.