From global time to local physics

TL;DR

This paper compares global and local time choices in canonical gravity, showing their effects on scalar field dynamics in cosmology and revealing how global time influences evolving coupling constants.

Contribution

It introduces a comparison between global and local time in cosmological models, highlighting the impact on scalar field evolution and coupling constants.

Findings

Similar dynamics for global and local time on terrestrial scales

Global time induces a mechanism for evolving coupling constants

Differences become significant beyond terrestrial time scales

Abstract

Global time is a gauge or relational choice of time variable in canonical gravity. Local time is the time used in a flat patch of spacetime. We compare the dynamics of a scalar field with respect to choices of global time and Minkowski patch time in an expanding cosmology. Our main results are that evolutions starting from the same initial conditions are similar on the time scales of terrestrial experiments, and that global time leads to a mechanism for evolving coupling constants.