{"work":{"id":"081a5c35-17fb-4820-babf-cb9164748a63","openalex_id":null,"doi":null,"arxiv_id":"2205.07787","raw_key":null,"title":"Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A$^*$","authors":null,"authors_text":"Sunny Vagnozzi, Rittick Roy, Yu-Dai Tsai, Luca Visinelli, Misba Afrin, Alireza Allahyari","year":2022,"venue":"gr-qc","abstract":"Horizon-scale images of black holes (BHs) and their shadows have opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. We consider a wide range of well-motivated deviations from classical General Relativity (GR) BH solutions, and constrain them using the Event Horizon Telescope (EHT) observations of Sagittarius A$^*$ (Sgr A$^*$), connecting the size of the bright ring of emission to that of the underlying BH shadow and exploiting high-precision measurements of Sgr A$^*$'s mass-to-distance ratio. The scenarios we consider, and whose fundamental parameters we constrain, include various regular BHs, string-inspired space-times, violations of the no-hair theorem driven by additional fields, alternative theories of gravity, novel fundamental physics frameworks, and BH mimickers including well-motivated wormhole and naked singularity space-times. We demonstrate that the EHT image of Sgr A$^*$ places particularly stringent constraints on models predicting a shadow size larger than that of a Schwarzschild BH of a given mass, with the resulting limits in some cases surpassing cosmological ones. Our results are among the first tests of fundamental physics from the shadow of Sgr A$^*$ and, while the latter appears to be in excellent agreement with the predictions of GR, we have shown that a number of well motivated alternative scenarios, including BH mimickers, are far from being ruled out at present.","external_url":"https://arxiv.org/abs/2205.07787","cited_by_count":null,"metadata_source":"pith","metadata_fetched_at":"2026-07-09T09:36:09.253132+00:00","pith_arxiv_id":"2205.07787","created_at":"2026-05-10T01:04:50.667633+00:00","updated_at":"2026-07-09T09:36:09.253132+00:00","title_quality_ok":true,"display_title":"Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A$^*$","render_title":"Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A$^*$"},"hub":{"state":{"work_id":"081a5c35-17fb-4820-babf-cb9164748a63","tier":"hub","tier_reason":"10+ Pith inbound or 1,000+ external citations","pith_inbound_count":36,"external_cited_by_count":null,"distinct_field_count":3,"first_pith_cited_at":"2025-01-13T03:00:02+00:00","last_pith_cited_at":"2026-07-08T14:48:08+00:00","author_build_status":"not_needed","summary_status":"needed","contexts_status":"needed","graph_status":"needed","ask_index_status":"not_needed","reader_status":"not_needed","recognition_status":"not_needed","updated_at":"2026-08-23T14:29:32.947218+00:00","tier_text":"hub"},"tier":"hub","role_counts":[{"context_role":"background","n":18}],"polarity_counts":[{"context_polarity":"background","n":17},{"context_polarity":"unclear","n":1}],"runs":{},"summary":{},"graph":{},"authors":[]}}