The complementarity of the redshift drift

TL;DR

This paper explores how redshift drift measurements can reveal specific dark energy properties and distinguish between models with unique signatures, especially at low and intermediate redshifts.

Contribution

It introduces equations linking redshift drift to dark energy characteristics and identifies which models can be constrained by future measurements.

Findings

Redshift drift can detect sudden changes in dark energy equation of state.

Oscillating dark energy models produce distinctive redshift drift signatures.

Large low-redshift variations in dark energy are unobservable via redshift drift.

Abstract

We derive some basic equations related to the redshift drift and we show how some dark energy (DE) properties can be retrieved from it. We consider in particular three kinds of DE models which exhibit a characteristic signature in their redshift drift while no such signature would be present in their luminosity-distances: a sudden change of the equation of state parameter w_{DE} at low redshifts, oscillating DE and finally an equation of state with spikes at low redshifts. Accurate redshift drift measurements would provide interesting complementary probes for some of these models and for models with varying gravitational coupling. While the redshift drift would efficiently constrain models with a spike at z~1, the signature of the redshift drift for models with large variations at very low redshifts z<0.1 would be unobservable, allowing a large arbitrariness in the present expansion of the universe.