Effects of Eddington-inspired Born-Infeld Gravity on Black Hole Accretion

Abstract

Black holes offer a unique setting to test gravity in the strong-field regime, where deviations from General Relativity are expected to be most pronounced. We study how modified gravity changes the structure of an advection-dominated accretion flow (ADAF) around a supermassive black hole. The gravitational field governing the disc is described by a Paczyński--Wiita-like potential derived in Eddington-inspired Born--Infeld (EiBI) gravity, formulated \textit{à la} Palatini. We solve the ADAF-like equations for this potential and compare the radial profiles of the flow with those obtained for the standard Paczyński--Wiita potential. The largest difference appears in the gas density, which is several orders of magnitude higher in the EiBI case near the inner region and converges to the standard result at large radii. The specific angular momentum and temperature are lower in EiBI gravity, while the radial velocity differs mainly at large radii for both solution branches, $ s=-1$ and $+1$. The angular velocity and the disk aspect ratio $H/r$ change only slightly. These results show that EiBI gravity can modify the density structure of hot accretion flows in the strong-field regime, potentially providing observational discriminators.