Article
Astronomy & Astrophysics
Giacomo Mascher, Kyriakos Destounis, Kostas D. Kokkotas
Summary: This study examines the phenomenon of superradiance in black holes in dynamic galactic environments, finding that the frequency range of superradiance decreases when a positive cosmological constant is introduced, but the amplification factors remain high. Interestingly, resonant peaks are still induced by long-lived quasinormal resonances in the superradiant regime.
Article
Physics, Nuclear
Peng Liu, Chao Niu, Cheng-Yong Zhang
Summary: The study focused on the instability of regularized 4D charged Einstein-Gauss-Bonnet de-Sitter black holes under charged scalar perturbations. It was found that unstable modes satisfy the superradiant condition, but not all modes satisfying this condition are unstable. The instability occurs when the cosmological constant is small and the black hole charge is not too large.
Article
Astronomy & Astrophysics
Cheng-Yong Zhang, Peng Liu, Yun-Qi Liu, Chao Niu, Bin Wang
Summary: The study focuses on the fully nonlinear dynamics of spherically symmetric black hole spontaneous scalarization in Einstein-Maxwell-scalar theory. It is found that by adjusting the coupling function and black hole charge, the development and stabilization of hairy black holes can be influenced.
Article
Astronomy & Astrophysics
J. Ovalle, E. Contreras, Z. Stuchlik
Summary: The research indicates that the cosmological constant is deformed near a black hole, leading to a reexamination of the black hole solution and the proposal of a new, simpler and more geometrically rich solution. A detailed study of the new black hole solution was carried out, showing the impact of rotation on the curvature, and a conjecture was made regarding its possible implications on alternative theories.
Article
Physics, Multidisciplinary
Zhen-Ming Xu, Bin Wu, Wen-Li Yang
Summary: This study used Kramer's escape rate method to investigate the intensity of the phase transition between small and large black hole states. The results show that the phase transition of charged anti-de Sitter (AdS) black holes from small to large presents serious asymmetric features, and the process is dominated by the transition from a small to a large black hole. This study filled a research gap in stochastic process analysis of the first-order phase transition rate in AdS black holes.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2023)
Article
Astronomy & Astrophysics
Antoine Rignon-Bret, Carlo Rovelli
Summary: This study presents an exact solution to the Maxwell-Einstein equations, describing the collapse and bounce of a charged spherical mass at the same space location. The solution is locally isometric to the Reissner-Nordström metric and depends on seven parameters. It sheds light on the fate of black holes and discusses the potential effects of classical instabilities and Hawking radiation.
Article
Astronomy & Astrophysics
Rong-Gen Cai, Li Li, Hao-Tian Sun
Summary: This study investigates the instability of charged Gauss-Bonnet-de Sitter black holes under gravito-electromagnetic perturbations. The research uncovers gravitational instability in spacetime dimensions five and above and constructs the complete parameter space. Additionally, it suggests that the BF bound violation cannot fully account for the physical origin of instability in charged Gauss-Bonnet black holes.
Article
Physics, Particles & Fields
Jun-Huai Xu, Zi-Han Zheng, Ming-Jian Luo, Jia-Hui Huang
Summary: The research investigates the superradiant stability of a Kerr-Newman black hole and charged massive scalar perturbation, finding that under certain conditions, the system is superradiantly stable.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Tyler McMaken, Andrew J. S. Hamilton
Summary: In this paper, the Hawking radiation detected by an inertial observer in a Reissner-Nordstrom spacetime is analyzed, with a focus on the asymptotic behavior of the Hawking spectrum as the observer approaches the inner or outer horizon. Two different methods are used to analyze the Hawking flux: an effective temperature is calculated to quantify the redshift experienced by the observer, and the full Bogoliubov graybody spectrum is computed in analytically solvable regions. The results show that the effective Hawking temperature is finite and becomes negative at the event horizon for certain conditions, while it is always negative and infinite at the inner horizon.
Article
Astronomy & Astrophysics
Ran Li, Jin Wang
Summary: In this study, we analyze the Hawking radiation and P - v criticality of charged dynamical (Vaidya) black hole in AdS space. By examining the near horizon properties of scalar field, we determine the Hawking temperature of the dynamical charged AdS black hole. Our results show that the critical pressure, volume, and temperature relationship is modified by the dynamical nature of the black hole, while the critical exponents remain unaffected. Additionally, the P - v criticality of the charged dynamical AdS black hole will disappear if the rate of change of the black hole horizon exceeds the critical value.
Article
Physics, Particles & Fields
Yu-Ping An, Li Li
Summary: We have proven the absence of charged scalar hair for static black holes in de-Sitter spacetime between the event horizon and the cosmological horizon. The proof is not dependent on the assumption of spherical symmetry and allows for general non-minimal coupling functions and higher curvature term corrections. This result has implications for the possibility of spontaneous scalarization around charged de-Sitter black holes.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Yu-Peng Wang, Liang Ma, Yi Pang
Summary: We compute the Euclidean action of charged de Sitter black holes in the four-dimensional gravitational Euler-Heisenberg model, and find that it is controlled by the total entropy contributed by the black hole outer horizon and the cosmological horizon. The Euclidean action can be interpreted as the black hole production rate in de Sitter space for smooth configurations. We also observe that the 4-derivative couplings break the symmetry between the production rate of purely electric black holes and purely magnetic black holes, but electromagnetic duality induces a transformation on these couplings, mapping the physical quantities of one type of black hole to the other type while preserving the unitarity constraints.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Nuclear
Peng Liu, Chao Niu, Cheng-Yong Zhang
Summary: The linear instability of charged massless scalar perturbation in regularized 4D charged Einstein-Gauss-Bonnet-AdS black holes is studied by investigating their quasinormal modes. It is found that the instability is triggered by superradiance and becomes more pronounced with increasing Gauss-Bonnet coupling constant or black hole charge. Furthermore, decreasing the AdS radius leads to a more stable charged massless scalar perturbation.
Article
Physics, Multidisciplinary
Yubo Ma, Yang Zhang, Lichun Zhang, Yu Pan
Summary: The paper investigates the extended thermodynamics and entropic force of de Sitter space-time with charged Gauss-Bonnet black hole, providing insights into the characteristics of four-dimensional Gauss-Bonnet gravity. The results suggest that the interaction force between the black hole horizon and the cosmic horizon is composed of two parts, with one part proportional to the Gauss-Bonnet factor and the other part related to the ratio of the two horizons' positions.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Emil T. Akhmedov, Kirill V. Bazarov
Summary: In this paper, we study a quantum real massive scalar field in the de Sitter-Schwarzschild spacetime background. To make analytical progress, we focus on the two-dimensional case, assuming that the situation in four dimensions will be similar conceptually. We assume the quantum field to be in a thermal state, described by the Planckian distribution for the exact modes in the given geometry. We approximately calculate the expectation value of the stress-energy tensor near the cosmological and black hole horizons. It is found that the geometry is strongly modified by the quantum fluctuations of the matter fields, due to the backreaction from quantum fields with a generic temperature.
Article
Astronomy & Astrophysics
Stephen R. Green, Antoine Maillard, Luis Lehner, Steven L. Liebling
Article
Astronomy & Astrophysics
Stephen R. Green, Robert M. Wald
CLASSICAL AND QUANTUM GRAVITY
(2016)
Article
Astronomy & Astrophysics
Stephen R. Green, Stefan Hollands, Akihiro Ishibashi, Robert M. Wald
CLASSICAL AND QUANTUM GRAVITY
(2016)
Article
Astronomy & Astrophysics
Stephen R. Green, Stefan Hollands, Peter Zimmerman
CLASSICAL AND QUANTUM GRAVITY
(2020)
Article
Astronomy & Astrophysics
Vahid Toomani, Peter Zimmerman, Andrew Spiers, Stefan Hollands, Adam Pound, Stephen R. Green
Summary: This paper reanalyzes the point-particle problem in Kerr and proposes a new method for calculating the metric, namely the Teukolsky puncture scheme. This scheme allows for metric calculations in a more regular gauge and provides a first step towards second-order self-force calculations.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Astronomy & Astrophysics
Nestor Ortiz, Federico Carrasco, Stephen R. Green, Luis Lehner, Steven L. Liebling, John Ryan Westernacher-Schneider
Summary: The study focused on analyzing sky maps and light curves of gamma-ray emission from neutron stars in compact binaries and in isolation, exploring various magnetic field structures' impact on gamma-ray emission, and proposing a simple approximation for rapid exploration of binary magnetic field structures.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Multidisciplinary
Maximilian Dax, Stephen R. Green, Jonathan Gair, Jakob H. Macke, Alessandra Buonanno, Bernhard Schoelkopf
Summary: Using deep learning, unprecedented accuracy is achieved in rapid gravitational wave parameter estimation. Neural networks serve as surrogates for Bayesian posterior distributions, resulting in analysis of gravitational wave events with close quantitative agreement compared to standard inference codes. Trained with simulated data, the networks encode signal and noise models, enabling fast and accurate inference for detected gravitational wave events.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Maximilian Dax, Stephen R. Green, Jonathan Gair, Michael Purrer, Jonas Wildberger, Jakob H. Macke, Alessandra Buonanno, Bernhard Scholkopf
Summary: We combine amortized neural posterior estimation with importance sampling to achieve fast and accurate gravitational-wave inference. This approach addresses criticisms against deep learning for scientific inference by providing a corrected posterior, a performance diagnostic for proposal assessment, and an unbiased estimate of the Bayesian evidence. Our study of 42 binary black hole mergers shows a significant improvement in sample efficiency and reduction in statistical uncertainty, indicating the potential impact of this method in gravitational-wave inference and other scientific applications.
PHYSICAL REVIEW LETTERS
(2023)
Article
Astronomy & Astrophysics
Jonas Wildberger, Maximilian Dax, Stephen R. Green, Jonathan Gair, Michael Puerrer, Jakob H. Macke, Alessandra Buonanno, Bernhard Schoelkopf
Summary: Deep learning techniques for gravitational-wave parameter estimation provide a fast alternative to traditional samplers with comparable accuracy. By training a normalizing flow model, these approaches, such as DINGO, can represent the Bayesian posterior conditional on observed data and account for changing detector characteristics by conditioning on the noise power spectral density. This study develops a probabilistic model to forecast future noise power spectral densities, allowing the training of deep learning models with a longer temporal scope and enabling accurate inference throughout the third LIGO-Virgo observing run (O3) using a DINGO network.
Article
Astronomy & Astrophysics
Stephen R. Green, Stefan Hollands, Laura Sberna, Vahid Toomani, Peter Zimmerman
Summary: We introduce a symmetric and conserved bilinear form for Weyl scalar perturbations of Kerr. By combining this form with a suitable renormalization prescription involving complex r integration contours, we show that quasinormal modes are orthogonal in the bilinear form for different ol, m, n thorn. These properties rely on the Petrov type D character of Kerr and its t-phi reflection isometry, and can be used to set up a framework for nonlinear quasinormal mode coupling in Kerr.
Article
Astronomy & Astrophysics
Laura Sberna, Pablo Bosch, William E. East, Stephen R. Green, Luis Lehner
Summary: This paper investigates a nonlinear effect during the ringdown process, namely the absorption-induced mode excitation, which is found to be the dominant nonlinear effect. The study shows that this effect occurs within the nonadiabatic regime and proposes an estimation technique.
Article
Computer Science, Artificial Intelligence
Stephen R. Green, Jonathan Gair
Summary: The LIGO and Virgo gravitational-wave observatories have detected many exciting events over the past 5 years. In order to infer the system parameters of binary black hole systems, researchers have applied deep learning to learn non-iterative surrogate models for Bayesian posterior distributions, allowing for rapid and accurate estimation.
MACHINE LEARNING-SCIENCE AND TECHNOLOGY
(2021)
Article
Astronomy & Astrophysics
Stephen R. Green, Christine Simpson, Jonathan Gair
Article
Astronomy & Astrophysics
Pablo Bosch, Stephen R. Green, Luis Lehner, Hugo Roussille
