Black hole shadows in nonminimally coupled Weyl connection gravity
Abstract
We study black hole shadows in nonminimally coupled Weyl connection gravity, a metric-affine extension of general relativity in which spacetime is described by a metric and a Weyl vector field encoding non-metricity. Despite going beyond the Riemannian framework, the presence of a non-dynamical Weyl vector ensures second-order field equations. The theory admits Schwarzschild- and Reissner--Nordstr\"{o}m-like solutions modified by a Weyl integration constant that parametrizes deviations from General Relativity. By computing the corresponding shadow radii and confronting them with the Event Horizon Telescope constraints on Sgr A*, we place observational bounds on the Weyl parameter. Assuming an observer distance and requiring consistency at the level, we obtain (model I), (model II), and (model III). Our results show that present horizon-scale imaging already sets meaningful limits on spacetime non-metricity. This work highlights the power of black hole shadow observations as probes of extended gravitational dynamics and establishes a direct link between Weyl-based theories and current astrophysical data.
Cite
@article{arxiv.2603.08441,
title = {Black hole shadows in nonminimally coupled Weyl connection gravity},
author = {Cláudio Gomes and Margarida Lima and Francisco S. N. Lobo and Luís F. D. da Silva},
journal= {arXiv preprint arXiv:2603.08441},
year = {2026}
}
Comments
11 pages, 5 figures