Testing General Relativity with 21 cm intensity mapping

Understand

We investigate the prospects for constraining alternative theories of gravity with a typical near-term low-budget 21 cm intensity mapping experiment.

• We derive the 21 cm brightness temperature perturbation consistently in linear theory including all line-of-sight and relativistic effects.
• We uncover new terms that are a small correction on large scales, analogous to those recently found in the context of galaxy surveys.
• We then perform a Fisher matrix analysis of the B_0 parametrization of f(R) gravity, where B_0 is proportional to the square of Compton wavelength of the scalaron.