Lookback time bounds from energy conditions

Understand

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.