scholarly journals Formalism for testing theories of gravity using lensing by compact objects: Static, spherically symmetric case

2005 ◽  
Vol 72 (10) ◽  
Author(s):  
Charles R. Keeton ◽  
A. O. Petters
Keyword(s):  
Symmetric Case ◽  
Compact Objects ◽  
Spherically Symmetric ◽  
Theories Of Gravity

Study of some compact objects in R + 2βT gravity

2019 ◽  
Vol 28 (16) ◽  
pp. 2040005
Author(s):  
Arfa Waseem ◽  
M. Sharif
Keyword(s):  
Stellar System ◽  
Graphical Analysis ◽  
Compact Objects ◽  
Stellar Structure ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Star Models ◽  
Mit Bag Model ◽  
Text Model

The aim of this work is to examine the nature as well as physical characteristics of anisotropic spherically symmetric stellar candidates in the context of [Formula: see text] gravity. We assume that the fluid components such as pressure and energy density are related through MIT bag model equation-of-state in the interior of stellar system. In order to analyze the structure formation of some specific star models, the field equations are constructed using Krori–Barua solution in which the unknown constants are evaluated by employing observed values of radii and masses of the considered stars. We check the consistency of [Formula: see text] model through the graphical analysis of energy conditions as well as stability of stellar structure. It is found that our considered stars show viable as well as stable behavior for this model.

scholarly journals Exact Spherically Symmetric Solutions in Modified Gauss–Bonnet Gravity from Noether Symmetry Approach

Symmetry ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 68 ◽  
Author(s):  
Sebastian Bahamonde ◽  
Konstantinos Dialektopoulos ◽  
Ugur Camci
Keyword(s):  
Vector Fields ◽  
Selection Criterion ◽  
Alternative Theories Of Gravity ◽  
Spherically Symmetric ◽  
Lie Point Symmetries ◽  
Noether Symmetries ◽  
Symmetry Approach ◽  
Point Transformations ◽  
Spherically Symmetric Solutions ◽  
Theories Of Gravity

It is broadly known that Lie point symmetries and their subcase, Noether symmetries, can be used as a geometric criterion to select alternative theories of gravity. Here, we use Noether symmetries as a selection criterion to distinguish those models of f ( R , G ) theory, with R and G being the Ricci and the Gauss–Bonnet scalars respectively, that are invariant under point transformations in a spherically symmetric background. In total, we find ten different forms of f that present symmetries and calculate their invariant quantities, i.e., Noether vector fields. Furthermore, we use these Noether symmetries to find exact spherically symmetric solutions in some of the models of f ( R , G ) theory.

scholarly journals Beyond Einstein’s General Relativity: Hybrid metric-Palatini gravity and curvature-matter couplings

2020 ◽  
Vol 29 (13) ◽  
pp. 2030008 ◽  
Author(s):  
Tiberiu Harko ◽  
Francisco S. N. Lobo
Keyword(s):  
General Relativity ◽  
Human Mind ◽  
Compact Objects ◽  
Cosmic Acceleration ◽  
Modified Theories Of Gravity ◽  
Late Time ◽  
Gravitational Fields ◽  
Matter Coupling ◽  
Theories Of Gravity ◽  
Einstein’S General Relativity

Einstein’s General Relativity (GR) is possibly one of the greatest intellectual achievements ever conceived by the human mind. In fact, over the last century, GR has proven to be an extremely successful theory, with a well established experimental footing, at least for weak gravitational fields. Its predictions range from the existence of black holes and gravitational radiation (now confirmed) to the cosmological models. Indeed, a central theme in modern Cosmology is the perplexing fact that the Universe is undergoing an accelerating expansion, which represents a new imbalance in the governing gravitational equations. The cause of the late-time cosmic acceleration remains an open and tantalizing question, and has forced theorists and experimentalists to question whether GR is the correct relativistic theory of gravitation. This has spurred much research in modified theories of gravity, where extensions of the Hilbert–Einstein action describe the gravitational field, in particular, [Formula: see text] gravity, where [Formula: see text] is the curvature scalar. In this review, we perform a detailed theoretical and phenomenological analysis of specific modified theories of gravity and investigate their astrophysical and cosmological applications. We present essentially two largely explored extensions of [Formula: see text] gravity, namely: (i) the hybrid metric-Palatini theory; (ii) and modified gravity with curvature-matter couplings. Relative to the former, it has been established that both metric and Palatini versions of [Formula: see text] gravity possess interesting features but also manifest severe drawbacks. A hybrid combination, containing elements from both of these formalisms, turns out to be very successful in accounting for the observed phenomenology and avoids some drawbacks of the original approaches. Relative to the curvature-matter coupling theories, these offer interesting extensions of [Formula: see text] gravity, where the explicit nonminimal couplings between an arbitrary function of the scalar curvature [Formula: see text] and the Lagrangian density of matter, induces a nonvanishing covariant derivative of the energy-momentum tensor, which implies nongeodesic motion and consequently leads to the appearance of an extra force. We extensively explore both theories in a plethora of applications, namely, the weak-field limit, galactic and extragalactic dynamics, cosmology, stellar-type compact objects, irreversible matter creation processes and the quantum cosmology of a specific curvature-matter coupling theory.

scholarly journals General relativistic Poynting-Robertson effect to diagnose wormholes existence: Static and spherically symmetric case

2020 ◽  
Vol 101 (10) ◽  
Author(s):  
Vittorio De Falco ◽  
Emmanuele Battista ◽  
Salvatore Capozziello ◽  
Mariafelicia De Laurentis
Keyword(s):  
Symmetric Case ◽  
Spherically Symmetric ◽  
General Relativistic

scholarly journals Cure for unstable numerical evolutions of single black holes: Adjusting the standard ADM equations in the spherically symmetric case

2001 ◽  
Vol 64 (8) ◽  
Author(s):  
Bernard Kelly ◽  
Pablo Laguna ◽  
Keith Lockitch ◽  
Jorge Pullin ◽  
Erik Schnetter ◽  
...  
Keyword(s):  
Black Holes ◽  
Symmetric Case ◽  
Spherically Symmetric
Sign in / Sign up

Export Citation Format

Share Document