Does time exist in quantum gravity?

TL;DR

This paper explores the conceptual implications of quantum gravity on the nature of time, suggesting it may be fundamentally timeless and only approximately defined in classical limits, with entropy linked to universe size.

Contribution

It investigates the problem of time in quantum gravity using minimal assumptions, highlighting the fundamental timelessness and emergent nature of classical time.

Findings

Quantum gravity may be fundamentally timeless.

Semiclassical time is only an approximate concept.

Entropy correlates with the size of the Universe.

Abstract

Time is absolute in standard quantum theory and dynamical in general relativity. The combination of both theories into a theory of quantum gravity leads therefore to a "problem of time". In my essay I shall investigate those consequences for the concept of time that may be drawn without a detailed knowledge of quantum gravity. The only assumptions are the experimentally supported universality of the linear structure of quantum theory and the recovery of general relativity in the classical limit. Among the consequences are the fundamental timelessness of quantum gravity, the approximate nature of a semiclassical time, and the correlation of entropy with the size of the Universe.