The gravitational constant and the cosmic microwave background
This research investigates how a varying gravitational constant ($G$) during recombination affects CMB power spectra. It finds that $G$ primarily influences the diffusion damping scale ($\ell_{damp}$), not other scales like $\ell_A$. A specific ratio of these scales allows for a direct comparison between $G$ at recombination and its present-day value, providing a robust test for modified gravity theories.