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We study the strong gravitational lensing effect around rotating black holes in different gravity theories. By calculating the deflection angle of strong gravitational lensing, we evaluate the lensing observables including the image…

General Relativity and Quantum Cosmology · Physics 2022-09-20 Xiao-Mei Kuang , Zi-Yu Tang , Bin Wang , Anzhong Wang

Recent observational data from the Event Horizon Telescope (EHT) collaboration provide convincing realistic evidence for the existence of black hole rotation. From a phenomenological perspective, a recently proposed stable rotating regular…

General Relativity and Quantum Cosmology · Physics 2025-01-15 Chen-Hao Xie , Yu Zhang , Qi Sun , Qi-Quan Li , Peng-Fei Duan

We are interested in black holes in Loop Quantum Gravity (LQG). We study the simple model of static black holes: the horizon is made of a given number of identical elementary surfaces and these small surfaces all behaves as a spin-s system…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Etera R. Livine , Daniel R. Terno

The study of astrophysical phenomena like black hole shadows is an effective approach to properly understand the modified gravity and explore its validity. Motivated by recent astrophysical observations, we consider a black hole (BH) in…

General Relativity and Quantum Cosmology · Physics 2025-03-20 Khadije Jafarzade , Zeynab Bazyar , Mubasher Jamil

The Event Horizon Telescope (EHT) is a millimeter-wavelength, very-long-baseline interferometry (VLBI) experiment that is capable of observing black holes with horizon-scale resolution. Early observations have revealed variable…

High Energy Astrophysical Phenomena · Physics 2016-12-20 Junhan Kim , Daniel P. Marrone , Chi-kwan Chan , Lia Medeiros , Feryal Özel , Dimitrios Psaltis

The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in…

General Relativity and Quantum Cosmology · Physics 2020-10-05 Dimitrios Psaltis , Lia Medeiros , Pierre Christian , Feryal Ozel , Kazunori Akiyama , Antxon Alberdi , Walter Alef , Keiichi Asada , Rebecca Azulay , David Ball , Mislav Balokovic , John Barrett , Dan Bintley , Lindy Blackburn , Wilfred Boland , Geoffrey C. Bower , Michael Bremer , Christiaan D. Brinkerink , Roger Brissenden , Silke Britzen , Dominique Broguiere , Thomas Bronzwaer , Do-Young Byun , John E. Carlstrom , Andrew Chael , Chi-kwan Chan , Shami Chatterjee , Koushik Chatterjee , Ming-Tang Chen , Yongjun Chen , Ilje Cho , John E. Conway , James M. Cordes , Geoffrey B. Crew , Yuzhu Cui , Jordy Davelaar , Mariafelicia De Laurentis , Roger Deane , Jessica Dempsey , Gregory Desvignes , Jason Dexter , Ralph P. Eatough , Heino Falcke , Vincent L. Fish , Ed Fomalont , Raquel Fraga-Encinas , Per Friberg , Christian M. Fromm , Charles F. Gammie , Roberto García , Olivier Gentaz , Ciriaco Goddi , Jose L. Gomez , Minfeng Gu , Mark Gurwell , Kazuhiro Hada , Ronald Hesper , Luis C. Ho , Paul Ho , Mareki Honma , Chih-Wei L. Huang , Lei Huang , David H. Hughes , Makoto Inoue , Sara Issaoun , David J. James , Buell T. Jannuzi , Michael Janssen , Wu Jiang , Alejandra Jimenez-Rosales , Michael D. Johnson , Svetlana Jorstad , Taehyun Jung , Mansour Karami , Ramesh Karuppusamy , Tomohisa Kawashima , Garrett K. Keating , Mark Kettenis , Jae-Young Kim , Junhan Kim , Jongsoo Kim , Motoki Kino , Jun Yi Koay , Patrick M. Koch , Shoko Koyama , Michael Kramer , Carsten Kramer , Thomas P. Krichbaum , Cheng-Yu Kuo , Tod R. Lauer , Sang-Sung Lee , Yan-Rong Li , Zhiyuan Li , Michael Lindqvist , Rocco Lico , Jun Liu , Kuo Liu , Elisabetta Liuzzo , Wen-Ping Lo , Andrei P. Lobanov , Colin Lonsdale , Ru-Sen Lu , Jirong Mao , Sera Markoff , Daniel P. Marrone , Alan P. Marscher , Ivan Martí-Vidal , Satoki Matsushita , Yosuke Mizuno , Izumi Mizuno , James M. Moran , Kotaro Moriyama , Monika Moscibrodzka , Cornelia Muller , Gibwa Musoke , Alejandro Mus Mejías , Hiroshi Nagai , Neil M. Nagar , Ramesh Narayan , Gopal Narayanan , Iniyan Natarajan , Roberto Neri , Aristeidis Noutsos , Hiroki Okino , Hector Olivares , Tomoaki Oyama , Daniel C. M. Palumbo , Jongho Park , Nimesh Patel , Ue-Li Pen , Vincent Pietu , Richard Plambeck , Aleksandar PopStefanija , Ben Prather , Jorge A. Preciado-Lopez , Venkatessh Ramakrishnan , Ramprasad Rao , Mark G. Rawlings , Alexander W. Raymond , Bart Ripperda , Freek Roelofs , Alan Rogers , Eduardo Ros , Mel Rose , Arash Roshanineshat , Helge Rottmann , Alan L. Roy , Chet Ruszczyk , Benjamin R. Ryan , Kazi L. J. Rygl , Salvador Sanchez , David Sanchez-Arguelles , Mahito Sasada , Tuomas Savolainen , F. Peter Schloerb , Karl-Friedrich Schuster , Lijing Shao , Zhiqiang Shen , Des Small , Bong Won Sohn , Jason SooHoo , Fumie Tazaki , Remo P. J. Tilanus , Michael Titus , Pablo Torne , Tyler Trent , Efthalia Traianou , Sascha Trippe , Ilse van Bemmel , Huib Jan van Langevelde , Daniel R. van Rossum , Jan Wagner , John Wardle , Derek Ward-Thompson , Jonathan Weintroub , Norbert Wex , Robert Wharton , Maciek Wielgus , George N. Wong , Qingwen Wu , Doosoo Yoon , Andre Young , Ken Young , Ziri Younsi , Feng Yuan , Ye-Fei Yuan , Shan-Shan Zhao , the EHT Collaboration

Black holes described by the Kerr metric can have a theoretical maximum dimensionless spin parameter of $a_\bullet = 1$, but several effects may limit the maximum spin parameter in astrophysical systems. We perform general relativistic…

High Energy Astrophysical Phenomena · Physics 2026-04-23 Tegan A. Thomas , Angelo Ricarte , Cora Prather , Hyerin Cho

With the recent release of the black hole image of Sgr A* alongside the earlier image of M87*, one can achieve an in-depth understanding of gravitational physics at the horizon scale. According to the Event Horizon Telescope (EHT)…

General Relativity and Quantum Cosmology · Physics 2024-05-06 Khadije Jafarzade , Seyed Hossein Hendi , Mubasher Jamil , Sebastian Bahamonde

Black hole (BH) shadow observations and gravitational wave astronomy have become crucial approaches for exploring BH physics and testing gravitational theories in extreme environments. This paper investigates the charged black hole with…

General Relativity and Quantum Cosmology · Physics 2025-09-16 Lai Zhao , Meirong Tang , Zhaoyi Xu

We consider a Lorentz violating non-commutating Kerr-like spacetime and studied the superradiance effect and the shadow cast by the back hole. We extensively study the different aspects of the black hole associated with a generalized…

General Relativity and Quantum Cosmology · Physics 2022-04-22 Sohan Kumar Jha , Anisur Rahaman

The Event Horizon Telescope has produced resolved images of the supermassive black holes Sgr A* and M87*, which present the largest shadows on the sky. In the next decade, technological improvements and extensions to the array will enable…

Very strong evidence suggests that Sagittarius A*, a compact radio source at the center of the Milky Way, marks the position of a super massive black hole. The proximity of Sgr A* in combination with its mass makes its apparent event…

Astrophysics of Galaxies · Physics 2009-06-23 Vincent L. Fish , Sheperd S. Doeleman

Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87* shadow size to infer constraints on the physical charges…

General Relativity and Quantum Cosmology · Physics 2021-06-02 Prashant Kocherlakota , Luciano Rezzolla , Heino Falcke , Christian M. Fromm , Michael Kramer , Yosuke Mizuno , Antonios Nathanail , Hector Olivares , Ziri Younsi , Kazunori Akiyama , Antxon Alberdi , Walter Alef , Juan Carlos Algaba , Richard Anantua , Keiichi Asada , Rebecca Azulay , Anne-Kathrin Baczko , David Ball , Mislav Balokovic , John Barrett , Bradford A. Benson , Dan Bintley , Lindy Blackburn , Raymond Blundell , Wilfred Boland , Katherine L. Bouman , Geoffrey C. Bower , Hope Boyce , Michael Bremer , Christiaan D. Brinkerink , Roger Brissenden , Silke Britzen , Avery E. Broderick , Dominique Broguiere , Thomas Bronzwaer , Do-Young Byun , John E. Carlstrom , Andrew Chael , Chi-kwan Chan , Shami Chatterjee , Koushik Chatterjee , Ming-Tang Chen , Yongjun Chen , Paul M. Chesler , Ilje Cho , Pierre Christian , John E. Conway , James M. Cordes , Thomas M. Crawford , Geoffrey B. Crew , Alejandro Cruz-Osorio , Yuzhu Cui , Jordy Davelaar , Mariafelicia De Laurentis , Roger Deane , Jessica Dempsey , Gregory Desvignes , Sheperd S. Doeleman , Ralph P. Eatough , Joseph Farah , Vincent L. Fish , Ed Fomalont , Raquel Fraga-Encinas , Per Friberg , H. Alyson Ford , Antonio Fuentes , Peter Galison , Charles F. Gammie , Roberto Garcia , Olivier Gentaz , Boris Georgiev , Ciriaco Goddi , Roman Gold , Jose L. Gomez , Arturo I. Gomez-Ruiz , Minfeng Gu , Mark Gurwell , Kazuhiro Hada , Daryl Haggard , Michael H. Hecht , Ronald Hesper , Luis C. Ho , Paul Ho , Mareki Honma , Chih-Wei L. Huang , Lei Huang , David H. Hughes , Shiro Ikeda , Makoto Inoue , Sara Issaoun , David J. James , Buell T. Jannuzi , Michael Janssen , Britton Jeter , Wu Jiang , Alejandra Jimenez-Rosales , Michael D. Johnson , Svetlana Jorstad , Taehyun Jung , Mansour Karami , Ramesh Karuppusamy , Tomohisa Kawashima , Garrett K. Keating , Mark Kettenis , Dong-Jin Kim , Jae-Young Kim , Jongsoo Kim , Junhan Kim , Motoki Kino , Jun Yi Koay , Yutaro Kofuji , Patrick M. Koch , Shoko Koyama , Carsten Kramer , Thomas P. Krichbaum , Cheng-Yu Kuo , Tod R. Lauer , Sang-Sung Lee , Aviad Levis , Yan-Rong Li , Zhiyuan Li , Michael Lindqvist , Rocco Lico , Greg Lindahl , Jun Liu , Kuo Liu , Elisabetta Liuzzo , Wen-Ping Lo , Andrei P. Lobanov , Laurent Loinard , Colin Lonsdale , Ru-Sen Lu , Nicholas R. MacDonald , Jirong Mao , Nicola Marchili , Sera Markoff , Daniel P. Marrone , Alan P. Marscher , Ivan Marti-Vidal , Satoki Matsushita , Lynn D. Matthews , Lia Medeiros , Karl M. Menten , Izumi Mizuno , James M. Moran , Kotaro Moriyama , Monika Moscibrodzka , Cornelia Muller , Gibwa Musoke , Alejandro Mus Mejias , Hiroshi Nagai , Neil M. Nagar , Masanori Nakamura , Ramesh Narayan , Gopal Narayanan , Iniyan Natarajan , Joseph Neilsen , Roberto Neri , Chunchong Ni , Aristeidis Noutsos , Michael A. Nowak , Hiroki Okino , Gisela N. Ortiz-Leon , Tomoaki Oyama , Feryal Ozel , Daniel C. M. Palumbo , Jongho Park , Nimesh Patel , Ue-Li Pen , Dominic W. Pesce , Vincent Pietu , Richard Plambeck , Aleksandar PopStefanija , Oliver Porth , Felix M. Potzl , Ben Prather , Jorge A. Preciado-Lopez , Dimitrios Psaltis , Hung-Yi Pu , Venkatessh Ramakrishnan , Ramprasad Rao , Mark G. Rawlings , Alexander W. Raymond , Angelo Ricarte , Bart Ripperda , Freek Roelofs , Alan Rogers , Eduardo Ros , Mel Rose , Arash Roshanineshat , Helge Rottmann , Alan L. Roy , Chet Ruszczyk , Kazi L. J. Rygl , Salvador Sanchez , David Sanchez-Arguelles , Mahito Sasada , Tuomas Savolainen , F. Peter Schloerb , Karl-Friedrich Schuster , Lijing Shao , Zhiqiang Shen , Des Small , Bong Won Sohn , Jason SooHoo , He Sun , Fumie Tazaki , Alexandra J. Tetarenko , Paul Tiede , Remo P. J. Tilanus , Michael Titus , Kenji Toma , Pablo Torne , Tyler Trent , Efthalia Traianou , Sascha Trippe , Ilse van Bemmel , Huib Jan van Langevelde , Daniel R. van Rossum , Jan Wagner , Derek Ward-Thompson , John Wardle , Jonathan Weintroub , Norbert Wex , Robert Wharton , Maciek Wielgus , George N. Wong , Qingwen Wu , Doosoo Yoon , Andre Young , Ken Young , Feng Yuan , Ye-Fei Yuan , J. Anton Zensus , Guang-Yao Zhao , Shan-Shan Zhao , The EHT Collaboration

Loop Quantum Gravity (LQG) is a theory that proposes a way to model the behavior of the spacetime in situations where its atomic characteristic arises. Among these situations, the spacetime behavior near the Big Bang or black hole's…

General Relativity and Quantum Cosmology · Physics 2019-03-08 M. B. Cruz , C. A. S. Silva , F. A. Brito

The advent of the Event Horizon Telescope (EHT), a millimeter-wave very-long baseline interferometric array, has enabled spatially-resolved studies of the sub-horizon-scale structure for a handful of supermassive black holes. Among these,…

High Energy Astrophysical Phenomena · Physics 2014-03-05 Avery E. Broderick , Tim Johannsen , Abraham Loeb , Dimitrios Psaltis

In this paper we review and discuss some of the intriguing properties of the Galactic Center supermassive black hole candidate Sgr A*. Of all possible black hole sources, the event horizon of Sgr A*, subtends the largest angular scale on…

High Energy Astrophysical Phenomena · Physics 2015-05-20 Heino Falcke , Sera Markoff , Geoffrey C. Bower , Charles F. Gammie , Monika Moscibrodzka , Dipankar Maitra

In the research paper [1], the analytical solution of semi-classical rotating black holes (BH) in loop quantum gravity theory (LQG) is obtained, but an unknown function $H$ is still preserved. In this note, we obtain an expression for the…

General Relativity and Quantum Cosmology · Physics 2023-03-01 Zhaoyi Xu

The Event Horizon Telescope (EHT) image of M87* provides a direct test of strong-field gravity, measuring an angular shadow diameter $\theta_{d}=42\pm 3~\mu\mathrm{as}$ and a circularity deviation $\Delta C\leq 0.1$. Such observations allow…

General Relativity and Quantum Cosmology · Physics 2026-05-13 Kourosh Nozari , Milad Hajebrahimi , Sara Saghafi , G. Mustafa , Emmanuel N. Saridakis

We consider Loop Quantum Gravity(LQG) motivated $4D$ polymerized black hole and study shadow, quasinormal modes, and Hawking radiation. We obtain analytical expressions of photonsphere radius and shadow radius and study their qualitative…

General Relativity and Quantum Cosmology · Physics 2023-10-10 Sohan Kumar Jha

We investigate the radiative efficiency and jet power in the spacetime of a rotating black hole within the framework of loop quantum gravity (LQG), which includes an additional LQG parameter. The results show that as the LQG parameter…

General Relativity and Quantum Cosmology · Physics 2024-11-21 Zhengwei Cheng , Songbai Chen , Jiliang Jing