Redshift drift in a pressure-gradient cosmology

TL;DR

This paper derives a redshift drift formula for Stephani universes, revealing distinctive predictions that differ from LTB and standard cosmological models, with potential observational tests using future telescopes and gravitational wave detectors.

Contribution

It introduces a redshift drift formula for pressure-gradient Stephani universes and compares their predictions with LTB and $ ext{Lambda}$CDM models.

Findings

Stephani models show positive drift at low redshift.

Distinct redshift drift signatures differentiate Stephani, LTB, and $ ext{Lambda}$CDM models.

Potential for observational testing with future telescopes and gravitational wave observatories.

Abstract

We derive a redshift drift formula for the spherically symmetric inhomogeneous pressure Stephani universes which are complementary to the spherically symmetric inhomogeneous density Lema\^itre-Tolman-Bondi models. We show that there is a clear difference between redshift drift predictions for these two models as well as between the Stephani models and the standard $\Lambda$CDM Friedmann models. The Stephani models have positive drift values at small redshift and behave qualitatively (but not quantitatively) as the $\Lambda$CDM models at large redshift, while the drift for LTB models is always negative. This prediction may perhaps be tested in future telescopes such as European Extremely Large Telescope (EELT), Thirty Meter Telescope (TMT), Giant Magellan Telescope (GMT), and especially, in gravitational wave interferometers DECi-Hertz Interferometer Gravitational Wave Observatory and Big Bang Observer (DECIGO/BBO), which aim at low redshift.