Cosmology on the Largest Scales with the SKA

TL;DR

The paper discusses how the SKA will enable unprecedented cosmological observations on ultra-large scales, testing fundamental physics like non-Gaussianity and gravity modifications with high precision.

Contribution

It highlights the potential of SKA to probe the largest cosmic scales, providing new insights into primordial non-Gaussianity and gravity beyond general relativity.

Findings

SKA can constrain primordial non-Gaussianity more tightly.

SKA will test gravity modifications on super-horizon scales.

Ultra-large scale observations are unaffected by baryonic feedback.

Abstract

The study of the Universe on ultra-large scales is one of the major science cases for the Square Kilometre Array (SKA). The SKA will be able to probe a vast volume of the cosmos, thus representing a unique instrument, amongst next-generation cosmological experiments, for scrutinising the Universe's properties on the largest cosmic scales. Probing cosmic structures on extremely large scales will have many advantages. For instance, the growth of perturbations is well understood for those modes, since it falls fully within the linear regime. Also, such scales are unaffected by the poorly understood feedback of baryonic physics. On ultra-large cosmic scales, two key effects become significant: primordial non-Gaussianity and relativistic corrections to cosmological observables. Moreover, if late-time acceleration is driven not by dark energy but by modifications to general relativity, then such modifications should become apparent near and above the horizon scale. As a result, the SKA is forecast to deliver transformational constraints on non-Gaussianity and to probe gravity on super-horizon scales for the first time.