Related references
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Article
Physics, Multidisciplinary
Grigoris Panotopoulos et al.
Summary: This article investigates the possibility of compact charged spheres made of a charged perfect fluid in the context of the 4D Einstein-Gauss-Bonnet (EGB) gravity theory. By rescaling the Gauss-Bonnet (GB) coupling constant and redefining gravity in 4D, the GB term contributes to the gravitational dynamics. The analysis is based on a polytropic equation of state and a proportional relation between charge density and energy density. The article derives hydrostatic equilibrium equations and solves them numerically to obtain mass-radius relations for charged compact stars. It also explores the relationship between mass and central mass density, as well as the relation between electric charge and maximum mass of compact stars in this gravity theory. The article concludes that charged stars may exist in nature and their deviation from traditional models may be observable in future astrophysical probes.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Physics, Particles & Fields
Takol Tangphati et al.
Summary: Gravitational-waves data have been widely used to test preferred modified gravity theories, and in this study, the possibility of testing them in the strong gravity regime by looking at the properties of compact objects in dense matter physics was investigated. The existence of quark stars in the color-flavor-locked phase of color superconductivity was predicted, and the focus was on aspects such as mass-radius profile, mass-central mass density relation, compactness, and the effective adiabatic index for stability-related issues. The predicted properties of quark stars were found to be consistent with observational data from GW 190814, allowing for constraints to be imposed on theoretical models of dense nuclear matter.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Multidisciplinary
Sudan Hansraj et al.
Summary: By exploiting curvature coordinates, new classes of exact solutions, including one that satisfies the required features of closed compact astrophysical objects, are discovered. The analysis reduces to a single first-order nonlinear differential equation, allowing the determination of a single integration constant through the matching of interior and exterior metrics. By invoking the second matching condition, the value of the Gauss-Bonnet coupling constant can be constrained in terms of the mass and radius of the star. Stability, causality, and energy conditions are satisfied within a suitable parameter space. However, when attempting to specify the radially oriented potential, only a defective spacetime and the recovery of the interior Schwarzschild metric for an incompressible fluid sphere were obtained.
Article
Astronomy & Astrophysics
Sergei D. Odintsov et al.
Summary: By considering models within the framework of Gauss-Bonnet gravities with a non-minimally coupled scalar field, it was found that the Einstein-Gauss-Bonnet gravity theory can maintain the correct speed of propagation for gravitational waves. Comparison with observational data showed that these theories fit well the data and provide a well-behaved cosmological evolution, slightly better than the ΛCDM model in terms of goodness of fit.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Physics, Particles & Fields
F. Gomez et al.
Summary: We consider the five-dimensional Einstein-Gauss-Bonnet gravity and derive the corresponding field equations and solutions by choosing appropriate coefficients in the five-dimensional Lanczos-Lovelock gravity theory. The hyperbolicity of the equations of motion is discussed, and the implications of the compactification procedure in the cosmological solutions are studied. The same procedure is also applied to obtain four-dimensional gravity from five-dimensional AdS-Chern-Simons gravity and study its cosmological solutions. Some aspects of the construction of the four-dimensional gravity action, as well as a brief review of Lovelock gravity in 5D, are considered in an Appendix.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Masato Minamitsuji et al.
Summary: The article focuses on issues related to scalar coupling in Horndeski theories, discussing the existence and linear stability of neutron star solutions, as well as the impact of scalar field profiles. It explores the stability and properties of the theories based on specific coupling forms and upper limits of coupling constants.
Article
Physics, Particles & Fields
H. S. Vieira et al.
Summary: This paper examines the interaction between massless scalar fields and the gravitational field generated by a black hole solution in the 4-dimensional Einstein-Gauss-Bonnet gravity with a cosmological constant. Quasibound state frequencies of scalar fields for the spherically symmetric black hole are calculated, and their expression is obtained using the polynomial condition associated with the Heun functions. The stability of the systems is also demonstrated.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
S. K. Maurya et al.
Summary: In this study, the possibility of the existence of compact charged spheres made of a charged perfect fluid in five-dimensional spacetime within the framework of Einstein-Gauss-Bonnet theory was investigated. Using a systematic and direct approach called minimal geometric deformation, it was proven that the fluid must be anisotropic and an exact and physically acceptable solution was found.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Zhenwei Lyu et al.
Summary: In this paper, the authors focus on testing the Einstein-dilation Gauss-Bonnet gravity theory using recent gravitational wave observations. They derive upper bounds on the coupling constant of the theory by analyzing neutron star black hole binaries and binary black hole events. The authors also investigate the impact of higher-order corrections to the waveform phase on the bounds.
Article
Astronomy & Astrophysics
M. S. Churilova
Summary: A consistent 4D Einstein-Gauss-Bonnet theory of gravity was proposed, and quasinormal modes of the Dirac field for spherically symmetric asymptotically flat black holes were calculated. It was found that the real part of the quasinormal modes increased significantly, while the damping rate usually decreased as the coupling constant grew.
PHYSICS OF THE DARK UNIVERSE
(2021)
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Astronomy & Astrophysics
Seyed Ali Hosseini Mansoori
Summary: This study employs the new formalism of thermodynamic geometry to investigate phase transition points and critical behavior of a Gauss-Bonnet-AdS black hole in four-dimensional spacetime. The research finds that for four-dimensional neutral Gauss Bonnet black holes, repulsive interaction among black hole microstructures may exist at low temperatures, contrasting with the dominant attractive interaction in five-dimensional black holes.
PHYSICS OF THE DARK UNIVERSE
(2021)
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Astronomy & Astrophysics
S. K. Maurya et al.
Summary: Researchers have proposed an exact solution for compact stellar remnants depending on a specific spacetime geometry, conducting calculations within the framework of five-dimensional Einstein-Gauss-Bonnet gravity and exploring the physical properties of these stars based on the Gauss-Bonnet coupling constant. The exterior solutions have been matched to a Boulware-Deser solution, ensuring energy conditions hold and the speed of sound remains causal inside the star. Additionally, the dynamical stability of the stellar structure has been studied by considering adiabatic radial oscillations theory.
MODERN PHYSICS LETTERS A
(2021)
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S. Nojiri et al.
Summary: In this work, we address the ghost issue in F(R, G) gravity and propose a technique to eliminate ghost degrees of freedom. By introducing auxiliary scalar fields and employing the Lagrange multiplier technique, the theory can be ghost-free in the Einstein frame and used as a reconstruction technique for various cosmological evolutions of interest. We demonstrate how this reconstruction technique can realize several cosmologically interesting phenomenologies.
Article
Physics, Multidisciplinary
S. A. Venikoudis et al.
Summary: This paper investigates the inflationary phenomenology in a specific gravitational theory with logarithmic modifications, comparing the viability of different models and considering non-Gaussianities and observational indices in the calculations. The results show that the models are phenomenologically viable for a wide range of parameters, with the logarithmic term making a minor contribution to numerical calculations as expected.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Physics, Multidisciplinary
Takol Tangphati et al.
Summary: Observations of pulsars heavier than 2 solar masses have constrained the equation of state above nuclear saturation density. The internal structure of a neutron star, correlated with the equation of state, is an active area of investigation. The properties and stability of quark stars with a well-motivated quantum chromodynamics equation of state depend on the Gauss-Bonnet coupling strength.
Review
Astronomy & Astrophysics
Eleonora Di Valentino et al.
Summary: There are significant discrepancies in predictions of the Hubble constant, leading to various proposed solutions including new physics theories or modifications to existing cosmological models. Some solutions successfully reduce tension and improve agreement with data, while many others fail to do so, highlighting the need for further research and evidence.
CLASSICAL AND QUANTUM GRAVITY
(2021)
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Farruh Atamurotov et al.
Summary: The study reveals that the combined effect of the Gauss-Bonnet coupling parameter and black hole charge influences the motion trajectories of particles and photons near the black hole, leading to significant changes in the gravitational deflection angle. The deflection angle is larger when considering uniform plasma compared to non-uniform plasma. Additionally, the center of mass energy in collision processes for non-spinning and spinning particles is affected by the GB parameter and black hole charge.
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Takol Tangphati et al.
Summary: Recent progress in determining the masses and radii of neutron stars has led to strong constraints on the equation of state (EoS) above nuclear saturation density. A proposed anisotropic star model within Einstein-Gauss-Bonnet gravity theory suggests the possibility of obtaining maximal neutron star mass and supports the existence of other massive pulsars with common radii. The study also discusses the mass vs central mass density relation and stability characteristics in this gravity theory.
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Summary: The current trend in dense matter physics at high densities and low temperatures focuses on the behavior of a degenerate Fermi gas of quarks forming Cooper pairs, known as a color superconductor, in compact objects. The study explores the anisotropy of quark stars (QSs) and their maximum mass-radius relation in the context of 4D Einstein-Gauss-Bonnet (EGB) gravity, considering the effects of Gauss-Bonnet (GB) coupling constant on the mass-radius relation and mass-central mass density relation of QSs. The research also examines the influence of anisotropy on the equilibrium and stability of strange stars, as well as other properties of QSs related to compactness and binding energy, providing evidence for super-massive pulsars in 4D EGB gravity.
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Wenbin Lu et al.
Summary: The researchers propose that the GW190814 event may be a second-generation merger from a hierarchical triple system based on the component masses and rates of coalescence. Their model provides several predictions and areas for further research in understanding these types of systems in the universe.
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