Article
Astronomy & Astrophysics
Eugeny Babichev, Christos Charmousis, Mokhtar Hassaine, Nicolas Lecoeur
Summary: In arbitrary higher dimension, we consider the combination of Lovelock gravity and a scalar-tensor action built out of higher order operators and Euler densities. The existence of black hole solutions interpreted as stealth configurations within Lovelock gravity theory is shown. The stealth solutions can include a time-dependent scalar field despite the underlying theory being non shift symmetric. Also, a procedure to obtain a nonconformally invariant action in even dimensions from the considered theory is presented.
Article
Astronomy & Astrophysics
Adolfo Cisterna, Anibal Neira-Gallegos, Julio Oliva, Scarlett C. Rebolledo-Caceres
Summary: The study demonstrates that the Plebanski-Demianski spacetime remains a solution of general relativity when supplemented with both a conformally coupled scalar theory and quadratic curvature corrections. The research also involves obtaining new hairy black hole solutions and analytically extending specific metric spacetimes to produce healthy asymptotically AdS wormhole configurations.
Article
Physics, Particles & Fields
Qi Qi, Yuan Meng, Xi-Jing Wang, Xiao-Mei Kuang
Summary: This paper investigates the gravitational lensing effects in the weak and strong field limits of a static black hole with conformally coupled scalar field. The results show that the weak deflection angle can be enhanced/suppressed by the scalar hair compared to general relativity. In the strong field limit, the lensing observables are influenced by the scalar hair, and there is a degeneracy in the observables of the charged black hole with positive scalar hair and RN black hole.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Jose Barrientos, Adolfo Cisterna, Cristobal Corral, Marcelo Oyarzo
Summary: The paper presents novel regular Euclidean solutions to General Relativity with Maxwell and conformally coupled scalar fields. The authors analyze the metrics of the Eguchi-Hanson and Taub-NUT families and solve the field equations analytically. The solutions have nontrivial topology and the authors compute the Euler characteristic explicitly. They also investigate the modifications to the solutions in the presence of higher-curvature corrections that respect conformal invariance.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Shobhit Giri, Hemwati Nandan, Lokesh Kumar Joshi, Sunil D. Maharaj
Summary: This study examines the stability of circular orbits in a traversable wormhole spacetime and employs the Lyapunov stability approach to determine the motion characteristics of non-spinning test particles in this spacetime.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
Wen-Di Guo, Shao-Wen Wei, Yu-Xiao Liu
Summary: Seeking singularity free solutions are crucial for understanding black holes in the quantum level. A recent study successfully constructed a five-dimensional singularity free black hole/topological star. Through Kaluza-Klein reduction, a four-dimensional static spherically symmetric charged black hole with scalar hair was obtained. The shadow of this charged black hole with scalar hair was investigated for four types of observers, and it was found that the shadow size depends on the motion status of the observer and the plasma model.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Nuriddin Kurbonov, Javlon Rayimbaev, Mirzabek Alloqulov, Muhammad Zahid, Farrux Abdulxamidov, Ahmadjon Abdujabbarov, Mukhabbat Kurbanova
Summary: We investigate the dynamics of charged test particles around an electrically charged black hole in Einstein-Maxwell-scalar (EMS) gravity. The event horizon properties and the upper limit for the EMS theory parameters are explored. The effective potential, specific energy, and angular momentum of the particles are studied, as well as the effects of EMS parameter and black hole charge on innermost stable circular orbits (ISCOs). Additionally, we analyze synchrotron radiation and electric Penrose and Banados-Silk-West processes in the spacetime of the charged black hole.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Fil Simovic, Danny Fusco, Robert B. Mann
Summary: The thermodynamic properties of 3+1 dimensional black holes conformally coupled to a real scalar field in asymptotically de Sitter spacetimes were investigated using a Euclidean action approach. By treating the cosmological constant as a thermodynamic pressure in the extended phase space, phase transitions resembling Hawking-Page transitions were observed in the black hole solutions, with the existence of these transitions further depending on a specific cosmic censorship bound.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Mathematical
Tao Ju, Jeff Viaclovsky
Summary: We study the prescribed scalar curvature problem in a conformal class on orbifolds with isolated singularities. We prove a compactness theorem in dimension 4, and an existence theorem which holds in dimensions n >= 4. This problem is more subtle than the manifold case since the positive mass theorem does not hold for ALE metrics in general. We also determine the U(2)-invariant Leray-Schauder degree for a family of negative-mass orbifolds found by LeBrun.
COMMUNICATIONS IN MATHEMATICAL PHYSICS
(2023)
Article
Physics, Particles & Fields
S. Habib Mazharimousavi
Summary: A new exact wormhole solution along with a non-black hole naked singular branch solution are introduced in the Einstein-Maxwell-Scalar theory. Both solutions are massless and coincide with the vacuum Minkowski flat spacetime when the charge is zero. The wormhole solution seems to be the missing part of the class of solutions in the standard Einstein-Maxwell-Dilaton theory.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Wen-Di Guo, Qin Tan, Yu-Xiao Liu
Summary: This paper investigates the quasinormal modes of a charged black hole with scalar hair, obtaining the fundamental frequencies numerically and studying the effect of magnetic charge on the modes.
Article
Astronomy & Astrophysics
Pantelis S. Apostolopoulos
Summary: In this study, we propose a mechanism to solve the scalar field equations of motion (non-minimally coupled with gravity) in a spherically symmetric background using purely geometrical methods. We find that all spacetimes of Petrov type O (conformally flat) can be completely determined when they admit a gradient conformal vector field. It is demonstrated that the full group of scalar field equations reduces to a single equation that is solely dependent on the distance w=r2-t2.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Astronomy & Astrophysics
Shahar Hod
Summary: This study proves that charged rotating Kerr-Newman black holes can support bound-state charged-matter configurations made of minimally coupled massive-scalar fields, and these configurations have a compact lower bound.
Article
Physics, Particles & Fields
Thanasis Karakasis, Eleftherios Papantonopoulos, Zi-Yu Tang, Bin Wang
Summary: Exact black hole solutions in f(R) gravity with a conformally coupled self-interacting scalar field are reported in both asymptotically flat or (A)dS four-dimensional spacetime. The modified gravity parameter a cannot be set to zero in the solutions derived for both asymptotically flat and (A)dS models, with the self-interacting potential determined from the Klein-Gordon equation to preserve conformal invariance. The thermodynamics of the solutions is also studied.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Bruno J. Barros, Alvaro de la Cruz-Dombriz, Francisco S. N. Lobo
Summary: In this study, novel analytical solutions for static and spherically symmetric wormhole geometries threaded by an anisotropic distribution of matter conformally coupled to a scalar ghost field are presented. The dynamics of the scalar field and matter throughout the wormhole, as well as the role played by the nonminimal coupling, are explored. Furthermore, coupled ghosts in the presence of a scalar potential are considered, and the traversability conditions within such geometrical scheme are analyzed.