Time in quantum cosmology

TL;DR

This paper reviews the problem of defining time in quantum gravity, discusses two proposed solutions, and applies these ideas to quantum cosmology, which studies the universe as a whole within quantum gravity.

Contribution

It provides a concise review of the time problem in quantum gravity and explores its implications for quantum cosmology.

Findings

Identifies the core issues with time in quantum gravity

Discusses two proposed solutions to the problem

Applies these solutions to quantum cosmology

Abstract

Time in quantum gravity is not a well-defined notion, despite its central role in the very definition of dynamics. Using the formalism of quantum geometrodynamics, we shortly review the problem and illustrate it with two proposed solutions. Our main application is quantum cosmology -- the application of quantum gravity to the Universe as a whole.