Article
Astronomy & Astrophysics
Andrew DeBenedictis, Saga Ilijic, Marko Sossich
Summary: This paper studies the properties that the vacuum must have in the minimal extension of the teleparallel equivalent of general relativity. It is found that the mathematical conditions on the vacuum mimic those of general relativity and that certain restrictions on the existence of smooth horizons and singularities are necessary. The analysis also suggests that static spherical matter distributions may have extra restrictions on their spatial extent and stress-energy bounds to ensure the validity of vacuum solutions.
Article
Physics, Multidisciplinary
Sweeti Kiroriwal, Jitendra Kumar, S. K. Maurya, Sourav Chaudhary
Summary: In this study, we examined new spherically symmetric wormhole solutions in modified symmetric teleparallel gravity theory. Constructing traversable wormholes with physically reasonable energy conditions and investigating their stability, we found that violations of energy conditions in gravity theory provide a viable framework for the study of wormholes.
Article
Astronomy & Astrophysics
Wenyi Wang, Hua Chen, Taishi Katsuragawa
Summary: This study analyzes the theoretical solutions of f(Q) gravity, revealing restrictions on its functional form and studying the properties of Schwarzschild-like solutions in nontrivial f(Q) gravity.
Article
Astronomy & Astrophysics
Jacob Oost, Shinji Mukohyama, Anzhong Wang
Summary: In Einstein-aether theory, spherically symmetric spacetimes are studied in different coordinate systems, yielding exact vacuum solutions characterized by parameters. These solutions satisfy observational constraints, but possess singularities leading to spacetime becoming singular.
Article
Astronomy & Astrophysics
Masato Minamitsuji, Antonio De Felice, Shinji Mukohyama, Michele Oliosi
Summary: In this study, static and spherically symmetric solutions are investigated in the minimal theory of bigravity (MTBG). It is found that a pair of Schwarzschild-de Sitter spacetimes with different cosmological constants and black hole masses is a solution in the self-accelerating branch of MTBG, but not in the normal branch. It is also shown that the Schwarzschild-de Sitter solutions can become compatible with the normal branch by using different coordinates. Furthermore, it is confirmed that the self-accelerating branch of MTBG admits static and spherically symmetric general relativity solutions with matter written in the spatially flat coordinates, including neutron stars with arbitrary matter equations of state. Finally, it is demonstrated that nontrivial solutions in the self-accelerating branch are given by the Schwarzschild-de Sitter metrics written in nonstandard coordinates.
Article
Physics, Multidisciplinary
S. A. Mardan, Umm-e-Farva Moeed, I. Noureen, Adnan Malik
Summary: The main objective of this work is to develop a novel general framework for generating solutions of stellar models in f(R) theory of gravity with class one metric. Such framework is not available in the vicinity of f(R) gravity. The relations of anisotropy factor, which is based on radial and tangential pressure, serve as the main source of generating solutions. The linear equation of state and conformally flat condition for class one metric are used to develop a consistent system of differential equations. We conclude that it is possible to develop generating solutions for the systems in f(R) gravity.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
Antonio De Felice, Shinji Mukohyama, Masroor C. Pookkillath
Summary: Static, spherically symmetric solutions representing stars made of barotropic perfect fluid are studied in the context of two theories of type-II minimally modified gravity, VCDM and VCCDM. It is found that the solutions in V(C)CDM exactly coincide with the ones in GR.
Article
Astronomy & Astrophysics
Alexey Golovnev, Maria-Jose Guzman
Summary: We study the properties of static spherically symmetric solutions in f(T) gravity by generalizing Bianchi identities and reducing the search for solutions to two simple equations. One equation is independent of the function f and describes the properties of solutions in any f(T) theory, while the other is the radial equation that identifies which function f is suitable for a chosen solution. Using these equations, we find exact and perturbative solutions for arbitrary and specific choices of f.
Article
Physics, Multidisciplinary
Mou Xu, Jianbo Lu, Shining Yang, Hongnan Jiang
Summary: The study explores the correction of thermodynamic entropy for a spherically symmetric black hole under the modified gravity theory called generalized Brans-Dicke theory. The effect of the entropy-correction term on the entropy is significant for small event horizon radii, but becomes negligible for larger values. Additionally, the heat capacity of black holes in the GBD theory undergoes a phase transition from negative to positive values as the event horizon radius increases.
Article
Astronomy & Astrophysics
Vasilisa Nikiforova
Summary: The study investigates time-dependent spherically symmetric perturbations of Schwarzschild black holes within torsion bigravity. Linearized perturbations are reduced to a Zerilli-like equation, where the potential structure implies the restriction of spin-2 excitation range to avoid singularities and the proof of linear stability of Schwarzschild black hole against spherically symmetric perturbations.
Article
Physics, Particles & Fields
Yuhma Asano, Harold C. Steinacker
Summary: We present a systematic study of spherically symmetric vacuum solutions of the IKKT matrix model within the framework of semi-classical covariant quantum geometries. We find all asymptotically flat solutions explicitly, which reproduce the linearized Schwarzschild geometry for large r but deviate from it at the non-linear level, including contributions from dilaton and axion. These solutions are relevant to the pre-gravity theory arising on classical brane solutions within the classical matrix model, and we also address the problem of reconstructing matrix configurations corresponding to a given frame.
Article
Physics, Particles & Fields
Marco Calza, Lorenzo Sebastiani
Summary: In this paper, we analyze a class of topological static spherically symmetric vacuum solutions in Q-gravity. We consider an Ansatz that ensures these solutions trivially satisfy the field equations when the non-metricity scalar is constant. Specifically, we provide and discuss local solutions in the form of black holes and traversable wormholes.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
R. Chan, M. F. A. da Silva, V. H. Satheeshkumar
Summary: The text analyzes all possible spherically symmetric exterior vacuum solutions allowed by the Einstein-Aether theory with static aether. Three classes of solutions are identified based on different values of a combination of free parameters, with explicit analytical solutions provided for specific cases. There are singularities present in some solutions while others are asymptotically flat spacetimes without horizons. This characteristic is different from general relativity. Additionally, the thermodynamics for the case where a horizon exists is briefly discussed.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Sebastian Murk, Daniel R. Terno
Summary: The existence of black holes, a key prediction of general relativity, is an important consistency test for modified gravity theories. This study derived constraints that any self-consistent modified theory of gravity must satisfy to be compatible with the existence of black holes. The properties and characteristic features of these black holes were analyzed using the Starobinsky model, with both solutions in general relativity considered as zeroth-order terms in perturbative solutions.
Article
Astronomy & Astrophysics
Michele Lenzi, Carlos F. Sopuerta
Summary: The perturbation theory of vacuum spherically symmetric spacetimes allows for an expansion of perturbations in scalar, vector, and tensor harmonics, with decoupled perturbative equations for modes with different parity and harmonic numbers. The most general master function for each parity is a linear combination of specific master functions, satisfying wave equations with potential. The study reveals two branches of solutions for each parity, one containing known master functions and the other including new master functions and an infinite collection of potentials leading to independent master functions.
Article
Physics, Particles & Fields
Thiago R. P. Carames, Julio C. Fabris, E. R. Bezerra de Mello, H. Belich
EUROPEAN PHYSICAL JOURNAL C
(2017)
Article
Physics, Particles & Fields
J. C. Fabris, Thiago R. P. Carames, J. M. Hoff da Silva
EUROPEAN PHYSICAL JOURNAL C
(2018)
Article
Astronomy & Astrophysics
Julio C. Fabris, Hermano Velten, Thiago R. P. Carames, Matheus J. Lazo, Gastao S. F. Frederico
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2018)
Article
Physics, Particles & Fields
Thiago R. P. Carames, Mahamadou H. Daouda, Julio C. Fabris, Adriano M. Oliveira, Oliver F. Piattella, Vladimir Strokov
EUROPEAN PHYSICAL JOURNAL C
(2014)
Article
Astronomy & Astrophysics
T. R. P. Carames, M. E. X. Guimaraes, J. M. Hoff da Silva
Article
Astronomy & Astrophysics
Hermano E. S. Velten, Thiago R. P. Carames
Article
Astronomy & Astrophysics
Thiago R. P. Carames, Julio C. Fabris, Hermano E. S. Velten
Article
Astronomy & Astrophysics
Hermano Velten, Thiago R. P. Carames, Juio C. Fabris, Luciano Casarini, Ronaldo C. Batista
Article
Physics, Particles & Fields
E. A. F. Braganca, Thiago R. P. Carames, Julio C. Fabris, Antonio de Padua Santos
EUROPEAN PHYSICAL JOURNAL C
(2019)
Article
Physics, Nuclear
J. C. Fabris, T. R. P. Carames, A. Wojnar, H. E. S. Velten
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2020)
Review
Astronomy & Astrophysics
Hermano Velten, Thiago R. P. Carames
Summary: Extended theories of gravity beyond the conservative framework of general relativity have become popular in recent years, aiming to describe the phenomenology of dark matter and dark energy. While many of these theories attempt to preserve the conservative property of the energy-momentum tensor, some unavoidably have non-trivial conservation laws as part of their structure when no extra constraint is available.
Article
Physics, Particles & Fields
Thiago R. P. Carames, J. M. Hoff da Silva
EUROPEAN PHYSICAL JOURNAL C
(2020)
Article
Astronomy & Astrophysics
Hermano Velten, Thiago R. P. Carames
Article
Astronomy & Astrophysics
Hermano Velten, Humberto A. Borges, Thiago R. P. Carames
Article
Astronomy & Astrophysics
Thiago R. P. Carames, H. Velten, J. C. Fabris, Matheus J. Lazo