21 cm Power Spectrum for Bimetric Gravity and its Detectability with SKA1-Mid Telescope

Abstract

We consider a modified gravity theory through a special kind of ghost-free bimetric gravity, where one massive spin-2 field interacts with a massless spin-2 field. In this bimetric gravity, the late time cosmic acceleration is achievable. Alongside the background expansion of the Universe, we also study the first-order cosmological perturbations and probe the signature of the bimetric gravity on large cosmological scales. One possible probe is to study the observational signatures of the bimetric gravity through the 21 cm power spectrum. We consider upcoming SKA1-mid antenna telescope specifications to show the prospects of the detectability of the ghost-free bimetric gravity through the 21 cm power spectrum. Depending on the values of the model parameter, there is a possibility to distinguish the ghost-free bimetric gravity from the standard $\Lambda$CDM model with the upcoming SKA1-mid telescope specifications.