Article
Astronomy & Astrophysics
K. A. Bronnikov
Summary: Simpson and Visser proposed a phenomenological way to avoid space-time singularities by replacing a parameter corresponding to singularity with a nonzero expression. This method can lead to a regular minimum beyond a black hole horizon and potentially mimic quantum gravity effects. The authors applied this method to regularize various metrics and obtained exact solutions in general relativity.
Article
Astronomy & Astrophysics
Lucas G. Collodel, Daniela D. Doneva, Stoytcho S. Yazadjiev
Summary: This paper investigates the equatorial circular orbit structure of Kerr black holes with scalar hair (KBHsSH) and compares the results of solutions with the same spin parameter but different normalized charges. The prominent features of these solutions, arising from the combined bound system of a hole with an off-center, self-gravitating distribution of scalar matter, are highlighted. Furthermore, the existence of a conserved scalar charge leads to nonuniqueness in the parameter space.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Mohaddese Heydari-Fard, Hamid Reza Sepangi
Summary: This study aims to investigate the possibility of observationally testing Einstein-scalar-Gauss-Bonnet gravity in the presence of the Gauss-Bonnet term, by studying thin accretion disk properties around scalarized black holes. It was found that accretion disks around scalarized black holes are hotter and more luminous than in general relativity.
Article
Astronomy & Astrophysics
Alejandro Cruz-Osorio, Lucian Rezzolla, Fabio D. Lora-Clavijo, Jose Antonio Font, Carlos Herdeiro, Eugen Radu
Summary: We present a numerical study of relativistic Bondi-Hoyle-Lyttleton accretion onto a black hole with synchronized hair. The steady-state solutions obtained provide insights into the formation of black holes in the presence of ultralight scalar fields and the possible association between the shock-cone and quasi-periodic oscillations in X-ray light curves.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Particles & Fields
P. A. Gonzalez, Eleftherios Papantonopoulos, Joel Saavedra, Yerko Vasquez
Summary: This study considers the propagation of charged massive scalar fields in the background of Reissner-Nordstrom-de Sitter black holes and investigates the effect of the scalar field charge on the spectrum of quasinormal frequencies and the anomalous decay rate. The results show that the anomalous behavior also exists for charged massive scalar fields, and there is a critical value that leads to a reversal of this behavior. Additionally, there is a critical value of the charge parameter and the black hole charge, which increases with the cosmological constant, and beyond this critical value, the anomalous behavior of the decay rate can be avoided for the fundamental mode.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Yun Soo Myung
Summary: The study revisits the superradiant stability of Kerr-Newman black holes under a charged massive scalar perturbation and obtains a newly suitable potential which is not singular at the outer horizon. From the potential analysis, a condition for the superradiant stability of Kerr-Newman black holes is found.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
Guangzhou Guo, Peng Wang, Houwen Wu, Haitang Yang
Summary: This study investigates the time evolutions of charged scalar perturbations on the background of a charged hairy black hole. By analyzing the quasinormal modes extracted from the waveform of scalar perturbations, it is discovered that some quasinormal modes can be superradiantly amplified when trapped in a potential well between two potential peaks. These superradiant modes render the charged hairy black hole unstable against charged scalar perturbations.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Astronomy & Astrophysics
Edgardo Franzin, Stefano Liberati, Jacopo Mazza, Alex Simpson, Matt Visser
Summary: The recent development of rotating black-bounce-Kerr spacetimes has sparked interest in exploring black-bounce variants of the entire Kerr-Newman family. Specifically focusing on black-bounce-Reissner-Nordstrom and black-bounce-Kerr-Newman spacetimes, researchers have considered their deviation from the Kerr-Newman family in a controlled manner, discussing the existence of Killing tensor and the theoretical impact of non-zero electric charge on astrophysical black holes. Additionally, they have examined the interesting matter/energy content required by the black-bounce-Kerr-Newman solution within the framework of general relativity.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Yves Brihaye, Betti Hartmann
Summary: We study the black hole solutions with scalar hair in the Einstein-Maxwell theory coupled to a complex scalar field. We find that new solutions exist for sufficiently large gravitational coupling and sufficiently small electromagnetic coupling. The scalar hair takes the form of a spatially oscillating 'wave packet' and affects the space-time such that the Ricci and Kretschmann scalars show similar oscillations.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Physics, Particles & Fields
Yi-Li Wang, Xian-Hui Ge
Summary: This paper investigates the Einstein-Maxwell-Gauss-Bonnet-axion theory in 4-dimensional spacetime through a Kaluza-Klein-like process. By obtaining the dyonic black hole solution coupled with higher derivative terms, the behavior of shear viscosity to entropy density ratio at different temperatures is studied. It is found that the ratio of uncharged black holes violates a specific bound at low temperatures, and the main feature of this ratio remains almost unchanged in 4 dimensions.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Wei -Xiang Feng, Alessandro Parisi, Chian-Shu Chen, Feng-Li Lin
Summary: The article discusses the spike mass density profile of dark matter in a dark halo, by self-consistently solving the relativistic Bondi accretion of dark matter onto a black hole. The research findings show that within the self-gravitating regime, the spike density profile does not fit well with a single-power law but a double-power one.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Wei-Xiang Feng, Alessandro Parisi, Chian-Shu Chen, Feng-Li Lin
Summary: In this study, the spike mass density profile in a dark halo is considered by self-consistently solving the relativistic Bondi accretion of dark matter onto a non-spining black hole. It is found that the spike density profile cannot be well fitted by a single-power law, but a double-power one.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Gabriele Bozzola, Vasileios Paschalidis
Summary: Unlike energy and angular momentum, electric charge is conserved in mergers of charged black holes. This paper investigates the formation of naked singularities in quasicircular mergers of charged binary black holes. The theoretical model is extended to estimate the properties of the remnant left by these mergers, and numerical-relativity simulations validate the model's accuracy. The theoretical model suggests that while naked singularities cannot form following these mergers, remnants that are arbitrarily close to the extremal limit can be produced.
Article
Astronomy & Astrophysics
Hamid R. Bakhtiarizadeh
Summary: This study presents the construction of charged rotating black string solutions in four-dimensional Einsteinian cubic gravity for the first time, providing insights into their thermodynamic properties. The solutions are found to be completely regular at the horizon and satisfy the first law of thermodynamics. It is also observed that some solutions have positive specific heat, indicating thermodynamic stability.
Article
Physics, Particles & Fields
Shahar Hod
Summary: The study reveals the existence of a new form of spontaneously scalarized black-hole configurations, showing that highly charged Reissner-Nordstrom black holes can support thin matter shells made of massive scalar fields. A compact analytical formula for the resonance spectrum of the coupling parameter characterizing the bound-state charged-black-hole-thin-massive-scalar-shell cloudy configurations is derived. These static scalar shells can hover a finite distance above the black-hole horizon under certain conditions.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Astronomy & Astrophysics
Miguel Alcubierre, Juan Barranco, Argelia Bernal, Juan Carlos Degollado, Alberto Diez-Tejedor, Victor Jaramillo, Miguel Megevand, Dario Nunez, Olivier Sarbach
Summary: A new class of complex scalar field objects, called l-boson stars, was discovered as a generalization of boson stars. These new solutions have a shell-like structure with an internal "hole" and exhibit properties such as convergence to finite compactness and high anisotropy.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Review
Physics, Particles & Fields
K. G. Arun, Enis Belgacem, Robert Benkel, Laura Bernard, Emanuele Berti, Gianfranco Bertone, Marc Besancon, Diego Blas, Christian G. Bohmer, Richard Brito, Gianluca Calcagni, Alejandro Cardenas-Avendano, Katy Clough, Marco Crisostomi, Valerio De Luca, Daniela Doneva, Stephanie Escoffier, Jose Maria Ezquiaga, Pedro G. Ferreira, Pierre Fleury, Stefano Foffa, Gabriele Franciolini, Noemi Frusciante, Juan Garcia-Bellido, Carlos Herdeiro, Thomas Hertog, Tanja Hinderer, Philippe Jetzer, Lucas Lombriser, Elisa Maggio, Michele Maggiore, Michele Mancarella, Andrea Maselli, Sourabh Nampalliwar, David Nichols, Maria Okounkova, Paolo Pani, Vasileios Paschalidis, Alvise Raccanelli, Lisa Randall, Sebastien Renaux-Petel, Antonio Riotto, Milton Ruiz, Alexander Saffer, Mairi Sakellariadou, Ippocratis D. Saltas, B. S. Sathyaprakash, Lijing Shao, Carlos F. Sopuerta, Thomas P. Sotiriou, Nikolaos Stergioulas, Nicola Tamanini, Filippo Vernizzi, Helvi Witek, Kinwah Wu, Kent Yagi, Stoytcho Yazadjiev, Nicolas Yunes, Miguel Zilhao, Niayesh Afshordi, Marie-Christine Angonin, Vishal Baibhav, Enrico Barausse, Tiago Barreiro, Nicola Bartolo, Nicola Bellomo, Ido Ben-Dayan, Eric A. Bergshoeff, Sebastiano Bernuzzi, Daniele Bertacca, Swetha Bhagwat, Beatrice Bonga, Lior M. Burko, Geoffrey Compere, Giulia Cusin, Antonio da Silva, Saurya Das, Claudia de Rham, Kyriakos Destounis, Ema Dimastrogiovanni, Francisco Duque, Richard Easther, Hontas Farmer, Matteo Fasiello, Stanislav Fisenko, Kwinten Fransen, Jorg Frauendiener, Jonathan Gair, Laszlo Arpad Gergely, Davide Gerosa, Leonardo Gualtieri, Wen-Biao Han, Aurelien Hees, Thomas Helfer, Jorg Hennig, Alexander C. Jenkins, Eric Kajfasz, Nemanja Kaloper, Vladimir Karas, Bradley J. Kavanagh, Sergei A. Klioner, Savvas M. Koushiappas, Macarena Lagos, Christophe Le Poncin-Lafitte, Francisco S. N. Lobo, Charalampos Markakis, Prado Martin-Moruno, C. J. A. P. Martins, Sabino Matarrese, Daniel R. Mayerson, Jose P. Mimoso, Johannes Noller, Nelson J. Nunes, Roberto Oliveri, Giorgio Orlando, George Pappas, Igor Pikovski, Luigi Pilo, Geraint Pratten, Tomislav Prokopec, Hong Qi, Saeed Rastgoo, Angelo Ricciardone, Rocco Rollo, Diego Rubiera-Garcia, Olga Sergijenko, Stuart Shapiro, Deirdre Shoemaker, Alessandro Spallicci, Oleksandr Stashko, Leo C. Stein, Gianmassimo Tasinato, Andrew J. Tolley, Elias C. Vagenas, Stefan Vandoren, Daniele Vernieri, Rodrigo Vicente, Toby Wiseman, Valery Zhdanov, Miguel Zumalacarregui
Summary: This white paper summarizes the importance of LISA in the field of fundamental physics and discusses future research directions and connections with other working groups.
LIVING REVIEWS IN RELATIVITY
(2022)
Article
Astronomy & Astrophysics
Pedro V. P. Cunha, Carlos A. R. Herdeiro, Joao P. A. Novo
Summary: This paper investigates the motion of particles on spherical 1 + 3 dimensional spacetimes under certain assumptions. It explores the curves on a two-dimensional manifold, the optical and Jacobi manifolds for null and timelike curves respectively. The study uses auxiliary two-dimensional metrics to analyze circular geodesics and considers both null and timelike circular geodesics.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Astronomy & Astrophysics
Carlos A. R. Herdeiro, Eugen Radu
Summary: According to generic arguments, solutions of the Klein-Gordon and Proca equations can be treated as classical if their typical action satisfies certain conditions, which is reasonable for describing the properties of typical bosonic stars.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Astronomy & Astrophysics
Brandon Bautista-Olvera, Juan Carlos Degollado, Gabriel German
Summary: We investigated the motion of particles around a rotating regular black hole, focusing on the effects of the characteristic length parameter on their dynamics. By solving the equation of orbital motion, we discovered a fourth constant of motion that determines the orbits out of the equatorial plane, similar to the Kerr black hole. Through detailed analysis and numerical simulations, we compared the possible orbits with those in a Kerr spacetime and found differences when the black holes rotate slowly for large characteristic length parameter values.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Physics, Multidisciplinary
Pedro V. P. Cunha, Carlos Herdeiro, Eugen Radu, Nicolas Sanchis-Gual
Summary: Ultracompact objects with light rings but without an event horizon can mimic black holes in their strong gravity phenomenology. Through numerical simulations and the introduction of a novel technique, we confirm the instability triggered by the light rings and identify two possible outcomes: migration to nonultracompact configurations or collapse to black holes.
PHYSICAL REVIEW LETTERS
(2023)
Article
Astronomy & Astrophysics
Alejandro Cruz-Osorio, Lucian Rezzolla, Fabio D. Lora-Clavijo, Jose Antonio Font, Carlos Herdeiro, Eugen Radu
Summary: We present a numerical study of relativistic Bondi-Hoyle-Lyttleton accretion onto a black hole with synchronized hair. The steady-state solutions obtained provide insights into the formation of black holes in the presence of ultralight scalar fields and the possible association between the shock-cone and quasi-periodic oscillations in X-ray light curves.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Zeus S. Moreira, Haroldo C. D. Lima Jr, Luis C. B. Crispino, Carlos A. R. Herdeiro
Summary: In this study, we analyze the quasinormal modes (QNMs) of a Schwarzschild black hole with corrections motivated by Loop Quantum Gravity (LQG). The black hole exhibits a global structure of a black bounce, and the QNM frequency orbits in the complex plane are self-intersecting spiraling curves. The overall damping decreases with increasing LQG parameter, and the spectrum of the quantum corrected black hole shows an oscillatory pattern with possible QNMs having vanishing real part.
Article
Astronomy & Astrophysics
Marco Brito, Carlos Herdeiro, Eugen Radu, Nicolas Sanchis-Gual, Miguel Zilhao
Summary: We studied the time evolution of excited-scalar boson stars in general relativity coupled to a complex massive scalar field with quartic self-interactions. The stars with up to 10 radial nodes can be made dynamically stable for sufficiently large values of the self-interactions coupling constant lambda. The compactness of these solutions is insensitive to the number of radial nodes for large lambda and fixed frequency.
Article
Astronomy & Astrophysics
Carlos A. R. Herdeiro, Eugen Radu
Summary: We show that Einstein-scalar theories allow balanced static, neutral, asymptotically flat, double-black hole solutions with appropriate self-interactions. The solutions are scalar hairy versions of the double-Schwarzschild (or Bach-Weyl) solution, but regular on and outside the two horizons. The balancing repulsive force is provided by the scalar field.
Article
Astronomy & Astrophysics
Alejandro Aguilar-Nieto, Victor Jaramillo, Juan Barranco, Argelia Bernal, Juan Carlos Degollado, Dario Nunez
Summary: In this study, the effect of self-interaction on the distribution and lifetime of long-lived configurations of massive scalar fields around black holes is analyzed. The spatial distribution of quasistationary states may be larger when there is self-interaction compared to the noninteracting case. The contribution of self-interaction to the lifetime of the configurations is found to be subdominant.
Article
Astronomy & Astrophysics
Miguel Alcubierre, Juan Barranco, Argelia Bernal, Juan Carlos Degollado, Alberto Diez-Tejedor, Miguel Megevand, Dario Nunez, Olivier Sarbach
Summary: In this study, boson star configurations in quantum field theory are constructed using the semiclassical gravity approximation. The semiclassical Einstein-Klein-Gordon system is reduced to the Einstein-Klein-Gordon system for N complex classical scalar fields. Various types of boson star solutions, including l-boson stars and multistate boson stars, are obtained. These configurations arise naturally as quantum fluctuations of a single field describing a many-body system. The results have potential impact on direct detection experiments related to ultralight scalar field/fuzzy dark matter candidates.
Article
Astronomy & Astrophysics
Pedro Ildefonso, Miguel Zilhao, Carlos Herdeiro, Eugen Radu, Nuno M. Santos
Summary: In this study, dipolar self-interacting scalar boson stars are constructed and dynamically evolved in a model with sextic (or quartic) self-interactions. The domain of existence of dipolar Q-stars has a similar structure to that of fundamental monopolar stars in the same model. The evolutions show that the dipolar Q-stars exhibit similar dynamical properties: 1) in the Newtonian and relativistic branches, they are dynamically robust over longer time scales compared to dipolar stars without self-interactions; 2) in the middle branch, they migrate to either the Newtonian or the relativistic branch; 3) beyond the relativistic branch, they decay to black holes. Overall, these results strengthen the observation that self-interactions can mitigate dynamical instabilities of scalar boson star models.
Article
Astronomy & Astrophysics
Nuno M. Santos, Carlos A. R. Herdeiro, Eugen Radu
Summary: This study finds that in some models, scalarized BHs bifurcating from Reissner-Nordstrom and spinning BHs with synchronized hair bifurcating from Kerr do not have local thermodynamic stability.
Article
Astronomy & Astrophysics
P. Cunha, C. Herdeiro, E. Radu, Ya. Shnir
Summary: In this study, we construct and explore the equilibrium solution space of two nonspinning miniboson stars in fully nonlinear general relativity. We find that the equilibrium is reached through the balance between gravitational attraction and scalar mediated repulsion, enabled by a relative phase. We also propose a simple analytic model that qualitatively captures the variation of the proper distance between the stars with their mass.