Cosmological history in York time: inflation and perturbations

TL;DR

This paper explores the use of York time, based on constant mean extrinsic curvature, as a physically meaningful time coordinate in cosmology, analyzing inflation and perturbations differently from standard cosmological time.

Contribution

It provides a novel mathematical framework for understanding inflation and perturbations using York time, contrasting it with conventional cosmological timelines.

Findings

York time offers a distinct mathematical account of inflation and perturbations.

The cosmological York-timeline differs from the conventional timeline.

Insights into the physical interpretation of cosmological processes in York time.

Abstract

The constant mean extrinsic curvature on a spacelike slice may constitute a physically preferred time coordinate, `York time'. One line of enquiry to probe this idea is to understand processes in our cosmological history in terms of York time. Following a review of the theoretical motivations, we focus on slow-roll inflation and the freezing and Hubble re-entry of cosmological perturbations. We show how the mathematical account of these processes is distinct from the conventional account in terms of standard cosmological or conformal time. We also consider the cosmological York-timeline more broadly and contrast it with the conventional cosmological timeline.