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

cam.issuedOnline2022-05-27
dc.contributor.authorVagnozzi, Sunny
dc.contributor.authorVisinelli, Luca
dc.contributor.orcidVagnozzi, Sunny [0000-0002-7614-6677]
dc.date.accessioned2022-05-30T11:04:24Z
dc.date.available2022-05-30T11:04:24Z
dc.date.issued2022-05-27
dc.date.submitted2022-05-23
dc.date.updated2022-05-30T11:04:23Z
dc.description.abstractSeveral 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$^*$ and Sagittarius A$^*$ (Sgr A$^*$), using the size $r_{\rm sh}$ and deviation from circularity $\Delta \mathcal{C}$ of the BH shadow. For the case of the EHT image of Sgr A$^*$, 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$^*$ compared to M87$^*$. 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$^*$'s shadow. The latter is quoted to be $\lesssim 10\%$ as with M87$^*$, 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$^*$'s image will therefore mostly have to rely on $r_{\rm sh}$, whereas additional observables such as the photon ring and azimuthal angle lapse should soon be available and allow for novel tests.
dc.identifier.doi10.17863/CAM.85004
dc.identifier.eissn2515-5172
dc.identifier.issn2515-5172
dc.identifier.otherrnaasac7331
dc.identifier.otherac7331
dc.identifier.otheraas39667
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/337594
dc.languageen
dc.language.isoeng
dc.publisherAmerican Astronomical Society
dc.publisher.urlhttp://dx.doi.org/10.3847/2515-5172/ac7331
dc.subjectastro-ph.GA
dc.subjectastro-ph.GA
dc.subjectastro-ph.CO
dc.subjectgr-qc
dc.subjecthep-ph
dc.subjecthep-th
dc.titleNote on fundamental physics tests from black hole imaging: Comment on "Hunting for extra dimensions in the shadow of Sagittarius A$^*$"
dc.typeArticle
dcterms.dateAccepted2022-05-25
prism.issueIdentifier5
prism.publicationNameRes. Notes AAS
prism.volume6
rioxxterms.licenseref.urihttp://creativecommons.org/licenses/by/4.0/
rioxxterms.versionVoR
rioxxterms.versionofrecord10.3847/2515-5172/ac7331

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