Lookback time bounds from energy conditions

TL;DR

This paper derives model-independent bounds on the lookback time in cosmology using energy conditions in general relativity, and tests these bounds against galaxy age data, revealing violations of energy conditions in recent cosmic history.

Contribution

It introduces a method to constrain cosmic lookback time behavior using energy conditions without assuming specific cosmological models.

Findings

Energy conditions impose bounds on lookback time as a function of redshift.

Galaxy age data suggests violations of energy conditions in recent cosmic history.

Results are consistent with previous findings of energy condition violations.

Abstract

In general relativity, the energy conditions are invoked to restrict general energy-momentum tensors on physical grounds. We show that in the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) approach to cosmological modeling, where the energy and matter components of the cosmic fluid are unknown, the energy conditions provide model-independent bounds on the behavior of the lookback time of cosmic sources as a function of the redshift for any value of the spatial curvature. We also confront such bounds with a lookback time sample which is built from the age estimates of 32 galaxies lying in the interval $0.11 \lesssim z \lesssim 1.84$ and by assuming the total expanding age of the Universe to be $13.7 \pm 0.2$ Gyr, as obtained from current cosmic microwave background experiments. In agreement with previous results, we show that all energy conditions seem to have been violated at some point of the recent past of cosmic evolution.