Testing time-delayed cosmology

TL;DR

This paper explores the implications of applying a time-delayed Friedmann equation to late-time cosmology, analyzing its effects on cosmic evolution and perturbations, and assessing its consistency with observational data.

Contribution

It introduces the concept of late-time cosmological delay using the delayed Friedmann equation and investigates its observable signatures and statistical viability.

Findings

Late-time cosmic delay is consistent with Hubble and growth data.

Identifies observable imprints of derivative discontinuities in delay differential equations.

Bayesian analysis suggests the delay parameter is nonzero but not strongly ruled out.

Abstract

Motivated by the proposed time-delayed cosmology in the primordial inflationary era, we consider the application of the delayed Friedmann equation in the late-time Universe and explore some of its observable consequences. We study the background evolution predicted by the delayed Friedmann equation and determine the growth of Newtonian perturbations in this delayed background. We reveal smoking-gun imprints of time-delayed cosmology that can be traced to derivative discontinuities generic in delay differential equations. We show that a late-time cosmic delay is statistically consistent with Hubble expansion rate and growth data. Based on these observables, we compute a nonzero best estimate for the time delay parameter and find that the Bayesian evidence does not strongly rule out a late-time time delay but warrants the subject further study.