English

Black hole shadows in nonminimally coupled Weyl connection gravity

General Relativity and Quantum Cosmology 2026-03-10 v1

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 rO=4.1×1010Mr_O = 4.1\times 10^{10}M and requiring consistency at the 2σ2\sigma level, we obtain ω1011.7M\omega \gtrsim 10^{11.7}M (model I), ω1010.5M\omega \gtrsim 10^{10.5}M (model II), and ω1012M\omega \sim 10^{12}M (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.

Keywords

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

R2 v1 2026-07-01T11:10:25.839Z