A Future Test of Gravitation Using Galaxy Cluster Velocities

TL;DR

This paper proposes using galaxy cluster velocities, measured through the kinetic Sunyaev-Zeldovich effect, as a novel method to test the validity of general relativity on cosmological scales by comparing structure growth with expansion history.

Contribution

It introduces a new observational approach utilizing cluster velocities to test gravity theories, linking cosmic structure growth with expansion history.

Findings

Galaxy cluster velocities can be measured via the kinetic Sunyaev-Zeldovich effect.

Future surveys will have sufficient data to distinguish between general relativity and alternative theories.

The method provides a direct test of gravity on large scales.

Abstract

The accelerating expansion of the Universe at recent epochs has called into question the validity of general relativity on cosmological scales. One probe of gravity is a comparison of expansion history of the Universe with the history of structure growth via gravitational instability: general relativity predicts a specific relation between these two observables. Here we show that the mean pairwise streaming velocity of galaxy clusters provides a useful method of constraining this relation. Galaxy cluster velocities can be measured via the kinetic Sunyaev-Zeldovich distortion of the cosmic microwave background radiation; future surveys can provide large enough catalogs of cluster velocities to discriminate between general relativity and other proposed gravitational theories.