Qiao Yue | Searcharxiv

arXiv2026

Scalar-tensor-vector gravity theory is tested by black hole photon rings

This paper investigates the photon ring and shadow structure of the Reissner-Nordström black hole in the scalar-tensor-vector gravitational framework. The black hole is characterized by the ( MOG) parameter (α) and the charge (Q). The study finds that as (α) increases, the event horizon radius (r_h), photon sphere radius (r_{ph}), and critical impact parameter (b_{ph}) all increase, while these decrease as (Q) increases. The innermost stable circular orbit radius (r_{isco}) exhibits similar monotonic behavior. Ray-tracing shows that as (Q) increases, the impact parameter (b) interval between the lensing ring and photon ring widens; (b_{\text{ph}}) is non-degenerate, and the photon ring radius is uniquely determined by (α) and (Q). Using $EHT$ constraints on (SgrA^*) and (M87^*), the bounds on (α) and (Q) are derived. For (Q = 0), (0.5), and (1), the allowed ranges are (α\in [0, 0.06]), ([0, 0.11]), and ([0.19, 0.36]), respectively. Radiative simulations show that for fixed (Q), larger (α) leads to a larger, non-degenerate photon ring. The Schwarzschild case is approached only when both (α) and (Q) are small. This provides a computational basis for testing modified black holes and offers a non-degenerate observational criterion for distinguishing quantum gravity models, consistent with current $EHT$ data. Future observations with $ngEHT$ and multi-band polarization can further test this. The results suggest that studying the photon ring structure of a Reissner-Nordström black hole in scalar-tensor-vector gravity provides a unique optical diagnostic for potential quantum-gravity tests and black hole properties.

gr-qc↗

arXiv2025

Testing Extended Theories of Gravity via Black Hole Photon Rings

This research delves into the optical characteristics of stationary, spherically symmetric black holes. These black holes follow the Konoplya-Zhidenko deformation rule in arbitrary gravity theories. This research finds that the effects of $a_2$ and $b_2$ on photon orbital dynamics exhibit observational degeneracy, while $\varepsilon$ significantly governs photon capture characteristics. As $\varepsilon$ increases, the radius of the photon sphere $r_{\text{ph}}$ and the critical impact parameter $b_{\text{ph}}$, and the innermost stable circular orbit radius $r_{\text{isco}}$ all increase. The event horizon $ r_{\text{h}} $ corresponds to that of the Schwarzschild black hole, while the impact parameter range for the lens and photon rings is reduced. Black hole shadow and photon ring analyses across three emission models show that increasing $\varepsilon$ shifts the peak rightward while enlarging the photon ring radius. The closer $\varepsilon$ is to zero, the more the results approach the Schwarzschild case, the more the results approach the Schwarzschild case. Additionally, by combining EHT observational data on the shadow diameters of M87 and Sgr A*, we imposed constraints on the correlation parameter $\varepsilon$ in the theoretical model(at the confidence level anchored by $d_{\text{sh}}^{(M87^*)}$, the parameter $\varepsilon$ is confined to the interval $-0.09 \lesssim \varepsilon \lesssim 0.19$. For $d_{\text{sh}}^{(Sgr A^*)}$, the constraint on $\varepsilon$ is delineated as $-0.280 \lesssim \varepsilon \lesssim 0.047$). The results show that within the observationally allowed range of $\varepsilon$ (such as $[-0.04, 0.04]$), the characteristics of the black hole exhibit specific regularities with changes in $\varepsilon$.

gr-qc↗