Note on fundamental physics tests from black hole imaging: Comment on "Hunting for extra dimensions in the shadow of Sagittarius A${}^{\ast }$"

Abstract

Several works over the past years have discussed the possibility of testing fundamental physics using Very Long Baseline Interferometry horizon-scale black hole (BH) images, such as the Event Horizon Telescope (EHT) images of M87${}^{\ast }$ and Sagittarius A${}^{\ast }$ (Sgr A${}^{\ast }$), using the size $r_{\mathrm{sh}}$ and deviation from circularity $\Delta \mathcal{C}$ of the BH shadow. For the case of the EHT image of Sgr A${}^{\ast }$, limits on $\Delta \mathcal{C}$ are not available due to the sparse interferometric coverage of the 2017 observations, alongside the short variability timescale of Sgr A${}^{\ast }$ compared to M87${}^{\ast }$. Concerning this point, we comment on the results of a recent preprint which purports to have derived new limits on extra dimensions using the deviation from circularity of Sgr A${}^{\ast }$'s shadow. The latter is quoted to be $\lesssim 10\%$ as with M87${}^{\ast }$, based on the "similarity" of the two shadows: however, this is an incorrect assumption, invalidating the subsequent results. In the immediate future, the simplest tests of fundamental physics from Sgr A${}^{\ast }$'s image will therefore mostly have to rely on $r_{\mathrm{sh}}$, whereas additional observables such as the photon ring and azimuthal angle lapse should soon be available and allow for novel tests.

arXiv comment3 pages, no figures

References in corpus (18)

• A Large Mass Hierarchy from a Small Extra Dimension
• An Alternative to Compactification
• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• Viewing the Shadow of the Black Hole at the Galactic Center
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Calculating black hole shadows: Review of analytical studies
• Testing the rotational nature of the supermassive object M87* from the circularity and size of its first image
• Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole Images
• Hunting for extra dimensions in the shadow of M87*
• Constraints on black-hole charges with the 2017 EHT observations of M87*
• The Shadow of a Spherically Accreting Black Hole
• Silhouette of M87*: A new window to peek into the world of hidden dimensions
• Probing Axions with Event Horizon Telescope Polarimetric Measurements
• Evaluation of New Submillimeter VLBI Sites for the Event Horizon Telescope
• Photon Ring Autocorrelations
• Revisiting the shadow of braneworld black holes
• Constraining the tidal charge of brane black holes using their shadows

Cited by in corpus (11)

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• Probing the Lorentz Symmetry Violation Using the First Image of Sagittarius A*: Constraints on Standard-Model Extension Coefficients
• Quasinormal modes-shadow correspondence for rotating regular black holes
• Trinity of black hole correspondences: Shadows, quasinormal modes, graybody factors, and cautionary remarks
• Shadow of quantum extended Kruskal black hole and its super-radiance property
• Shadows and parameter estimation of rotating quantum corrected black holes and constraints from EHT observation of M87* and Sgr A*
• Hunting for extra dimensions in black hole shadows
• Motion of particles around a magnetically charged Euler-Heisenberg black hole with scalar hair and the Event Horizon Telescope
• Influence of Quantum Correction on Kerr Black Hole in Effective Loop Quantum Gravity via Shadows and EHT Results
• Thermodynamic and observational constraints on black holes with primary hair in Beyond Horndeski Gravity: Stability and shadows