  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.

Cosmology and Nongalactic Astrophysics;General Relativity and Quantum Cosmology