Speaker
Description
The inverse-square law of gravitation has been tested from microscopic to solar system scales. However, directly probing gravity at galactic and cosmological scales remains a challenge. At galactic scales, the missing mass dominates rotation curves, while extragalactic tests often depend on the assumed expansion history of the universe. These dependencies complicate model-agnostic tests of theories of gravity that seek to explain these phenomena without invoking dark matter. In this talk, I present the pairwise kinematic Sunyaev-Zeldovich (kSZ) effect (the Doppler-shifted Compton-scattered light of the cosmic microwave background) as a direct, model-independent probe of the gravitational force law. We show that modified gravity models capable of reproducing the observed correlation function of galaxies may still fail to predict their mean pairwise velocity. Using data from the Atacama Cosmology Telescope and the Sloan Digital Sky Survey we constrain the exponent n of the gravitational force scaling, g \propto r^{-n}. Our analysis covers distances from tens to two-hundred megaparsecs, representing the largest scale test of the gravitational force law to date. I will discuss how upcoming CMB surveys such as the Simons Observatory large aperture telescope, paired with large spectroscopic catalogs of galaxies such as DESI are poised to probe gravity with 10σ significance, establishing the kSZ effect as a probe of gravity.