Closing the cosmological loop with the redshift drift

TL;DR

This paper compares various methods for measuring the redshift drift to understand the universe's expansion, emphasizing that no single method is best for all scientific goals and that experiments should be optimized accordingly.

Contribution

It provides a comparative analysis of different redshift drift measurement techniques using Fisher Matrix and MCMC, highlighting their strengths and optimal applications.

Findings

No single measurement method outperforms others universally.

Performance depends on experimental parameters and scientific objectives.

Optimization of experiments is essential for specific cosmological goals.

Abstract

The redshift drift (also known as the Sandage Test) is a model-independent probe of fundamental cosmology, enabling us to watch the universe expand in real time, and thereby to confirm (or not) the recent acceleration of the universe without any model-dependent assumptions. On the other hand, by choosing a fiducial model one can also use it to constrain the model parameters, thereby providing a consistency test for results obtained with other probes. The drift can be measured by the Extremely Large Telescope and also by the full SKA. Recently two alternative measurement methods have been proposed: the cosmic accelerometer, and the differential redshift drift. Here we summarize a comparative analysis of the various methods and their possible outcomes, using both Fisher Matrix and MCMC techniques. We find that no single method is uniformly better than the others. Instead, their comparative performance depends both on experimental parameters (including the experiment time and redshift at which the measurement is made) and also on the scientific goal (e.g., detecting the drift signal with high statistical significance, constraining the matter density, or constraining the dark energy properties). In other words, the experiment should be optimized for the preferred scientific goal.