Definitive Test of the R_h=ct Universe Using Redshift Drift

TL;DR

Upcoming redshift drift measurements using ELT-HIRES and SKA could decisively test the R_h=ct cosmology by detecting zero drift, contrasting with variable expansion models like Planck LCDM, and potentially provide strong evidence for R_h=ct.

Contribution

This paper predicts a distinctive zero redshift drift signature for the R_h=ct universe, enabling a clear observational test to distinguish it from other cosmological models.

Findings

R_h=ct predicts zero redshift drift at all redshifts.

Planck LCDM predicts measurable negative drift at z=5.

Future measurements could differentiate models at 3-5 sigma significance.

Abstract

The redshift drift of objects moving in the Hubble flow has been proposed as a powerful model-independent probe of the underlying cosmology. A measurement of the first and second order redshift derivatives appears to be well within the reach of upcoming surveys using ELT-HIRES and the SKA Phase 2 array. Here we show that an unambiguous prediction of the R_h=ct cosmology is zero drift at all redshifts, contrasting sharply with all other models in which the expansion rate is variable. For example, multi-year monitoring of sources at redshift z=5 with the ELT-HIRES is expected to show a velocity shift Delta v = -15 cm/s/yr due to the redshift drift in Planck LCDM, while Delta v=0 cm/s/yr in R_h=ct. With an anticipated ELT-HIRES measurement error of +/-5 cm/s/yr after 5 years, these upcoming redshift drift measurements might therefore be able to differentiate between R_h=ct and Planck LCDM at ~3 sigma, assuming that any possible source evolution is well understood. Such a result would provide the strongest evidence yet in favour of the R_h=ct cosmology. With a 20-year baseline, these observations could favor one of these models over the other at better than 5 sigma.