Universal Bounds on Black Hole Observables Imposed by Energy Conditions
Abstract
Energy conditions (ECs) underpin fundamental results in general relativity, yet their observational validity in strong gravitational fields remains largely untested. Here, we establish a direct correspondence between the local stress-energy tensor, photon-orbit dynamics, and strong-field observables associated with black hole shadows, photon rings, and eikonal gravitational-wave ringdown for static, spherically symmetric black holes within general relativity. We show that imposing local ECs at unstable photon spheres yields analytic bounds on these observables. In particular, the demagnification of successive photon rings provides an exact diagnostic of the local tangential null energy condition. These bounds offer a direct route to constraining the matter fields sourcing spacetimes and testing ECs through strong-field observations. Combining them with observational measurements of these observables further restricts admissible black hole geometries and additionally constrains the otherwise inaccessible photon sphere geometry and local stress-energy content, demonstrating their observational potential in the strong-field regime.
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BibTeX
@misc{walia2026universal,
title = {{Universal Bounds on Black Hole Observables Imposed by Energy Conditions}},
author = {Rahul Kumar Walia and Boris Georgiev and Chi-kwan Chan},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2607.11840},
eprint = {2607.11840},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.11840},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Universal Bounds on Black Hole Observables Imposed by Energy Conditions
AU - Rahul Kumar Walia
AU - Boris Georgiev
AU - Chi-kwan Chan
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2607.11840
UR - https://arxiv.org/abs/2607.11840
AB - Energy conditions (ECs) underpin fundamental results in general relativity, yet their observational validity in strong gravitational fields remains largely untested. Here, we establish a direct correspondence between the local stress-energy tensor, photon-orbit dynamics, and strong-field observables associated with black hole shadows, photon rings, and eikonal gravitational-wave ringdown for static, spherically symmetric black holes within general relativity. We show that imposing local ECs at unstable photon spheres yields analytic bounds on these observables. In particular, the demagnification of successive photon rings provides an exact diagnostic of the local tangential null energy condition. These bounds offer a direct route to constraining the matter fields sourcing spacetimes and testing ECs through strong-field observations. Combining them with observational measurements of these observables further restricts admissible black hole geometries and additionally constrains the otherwise inaccessible photon sphere geometry and local stress-energy content, demonstrating their observational potential in the strong-field regime.
ER -