Review
Physics, Multidisciplinary
Jose W. Maluf, Fernando L. Carneiro, Sergio C. Ulhoa, Jose F. da Rocha-Neto
Summary: This article reviews the concept and definitions of energy-momentum and angular momentum in the gravitational field according to the teleparallel equivalent of general relativity (TEGR). It justifies the importance of these definitions based on the well-established formulation of the TEGR, the existence of the algebra of the Poincare group in its phase space, and the consistency of results obtained from numerous applications. The article also revisits the concept of localization of gravitational energy and demonstrates its validity through the behavior of free particles in plane fronted gravitational waves.
ANNALEN DER PHYSIK
(2023)
Article
Astronomy & Astrophysics
Keefe Mitman, Dante A. B. Iozzo, Neev Khera, Michael Boyle, Tommaso De Lorenzo, Nils Deppe, Lawrence E. Kidder, Jordan Moxon, Harald P. Pfeiffer, Mark A. Scheel, Saul A. Teukolsky, William Throwe
Summary: By using the BMS balance laws, the corrected strain waveforms in the SXS catalog now include the missing displacement memory and satisfy the laws to a higher degree of accuracy. These corrected waveforms show good agreement with waveforms exhibiting memory effects and avoid transient junk effects.
Article
Astronomy & Astrophysics
M. F. Mourad, M. Abdelgaber
Summary: In this study, we investigate the energy-momentum localization of a stringy charged black hole using two different approaches, Bergman-Thompson's prescription and Papapetrou's prescription, within the frameworks of general relativity and teleparallel equivalent to GR. The results are consistent with previous studies, and we also calculate the gravitational energy-momentum flux and center of mass in TEGR.
MODERN PHYSICS LETTERS A
(2022)
Article
Physics, Mathematical
Richard James Petti
Summary: This paper derives the elements of classical Einstein-Cartan theory (EC) from classical general relativity (GR) in two ways: using one Kerr solution in GR and a distribution of many Kerr masses in GR. The limitations in convergence computations restrict the limits from continuing to an infinitesimal length scale, impacting the derivation of EC from GR. EC enables modeling exchange of intrinsic and orbital angular momentum, strengthening the case for EC and new physics derived from EC.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2021)
Article
Physics, Particles & Fields
Markus B. Froeb
Summary: Research shows that the Kerr-Schild ansatz can be extended into different gravity theories, with solutions depending differently on the choice of tetrad in the framework.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Multidisciplinary
Abdelghani Errehymy, Allah Ditta, G. Mustafa, S. K. Maurya, Abdel-Haleem Abdel-Aty
Summary: This paper investigates the properties of electrically charged strange stars in f(Q) symmetric teleparallel gravity, using the MIT-Bag model equation of state to control the distribution of strange quark matter. The radii of compact star candidates are predicted and their physical viability and stability are tested.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Physics, Multidisciplinary
G. G. L. Nashed, Kazuharu Bamba
Summary: In this study, an interior solution of a physically symmetric vierbein with two unknown functions in conformal teleparallel gravity was explored, leading to a new set of configurations consistent with observed pulsars. The model was applied to the pulsar 4U 1608-52 and stability analysis was performed by studying causality conditions and adiabatic index. Additionally, the consistency of the model with other pulsars was investigated.
PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS
(2022)
Article
Astronomy & Astrophysics
Jose Beltran Jimenez, Tomi S. Koivisto
Summary: The Noether currents are derived in a generic metric-affine theory of gravity, and the holographic nature of the gravitational entropy and energy-momentum is clarified. The main result is the verification of the canonical resolution to the energy-momentum problem in the Noether formalism.
Article
Astronomy & Astrophysics
Ritesh Bachhar, Richard H. Price, Gaurav Khanna
Summary: Studying the transfer of angular momentum and tidal coupling in the inspiral and merger of black holes is crucial for understanding their interactions. This research presents an expression that accurately describes the orbital angular momentum of a binary system in the regime of small separations.
Article
Astronomy & Astrophysics
Adam Freese
Summary: This study obtains the energy-momentum tensor for quantum electrodynamics and quantum chromodynamics through Noether's second theorem, and it has automatic symmetry and invariance.
Article
Astronomy & Astrophysics
Keefe Mitman, Leo C. Stein, Michael Boyle, Nils Deppe, Francois Hebert, Lawrence E. Kidder, Jordan Moxon, Mark A. Scheel, Saul A. Teukolsky, William Throwe, Nils L. Vu
Summary: Fixing the entire BMS freedom of NR waveforms to match the frame of either PN waveforms or black hole perturbation theory is crucial, and can be achieved by finding the BMS transformations that change certain charges.
Article
Physics, Multidisciplinary
Manuel Hohmann
Summary: This paper discusses linear perturbations of teleparallel spacetimes with cosmological symmetry and decomposes them into irreducible components. The behavior of these perturbations under gauge transformations is studied, leading to the derivation of a complete set of gauge-invariant perturbation variables. Comparing the results with perturbations around a diagonal tetrad corresponding to a spatially flat teleparallel background cosmology reveals the appearance of new terms dependent on the specific choice of a cosmologically symmetric background tetrad.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Astronomy & Astrophysics
Philip K. Schwartz
Summary: We discuss a teleparallel version of Newton-Cartan gravity, which arises as a large-speed-of-light limit of the teleparallel equivalent of general relativity (TEGR). It provides a geometric formulation of the Newtonian limit of TEGR, similar to how standard Newton-Cartan gravity is the Newtonian limit of general relativity. By a specific gauge-fixing, we show how the standard formulation of Newtonian gravity can be recovered.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Astronomy & Astrophysics
L. Herrera, A. Di Prisco, J. Ospino
Summary: A comprehensive study was conducted on static fluid distributions endowed with hyperbolic symmetry, revealing their negative energy density which requires extreme physical conditions where quantum effects play an important role. The inability of the fluid distribution to fill the region close to the center of symmetry was observed, with a vacuum cavity potentially representing that region. The positive defined mass function and negative Tolman mass calculations showcased the repulsive nature of gravitational interaction, with some exact analytical solutions provided as well.
Article
Physics, Particles & Fields
B. V. Ivanov
Summary: The expressions in the Einstein-Maxwell equations serve as generating functions for charged stellar models, incorporating equation of state and conformal motion conditions. The resulting equations are linear first order differential equations and Riccati equations, which can always be transformed into second order homogeneous linear differential equations.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
G. G. L. Nashed
Summary: The study investigates the non-trivial black hole solutions for neutral and charged spherically symmetric space-times, determines the metric potentials, and calculates the thermodynamic quantities for these black holes, showing consistency with existing literature. Additionally, the validity of the first law of thermodynamics for the black holes is demonstrated.
Article
Multidisciplinary Sciences
Prateek Sharma, Hemwati Nandan, Gamal G. L. Nashed, Shobhit Giri, Amare Abebe
Summary: This article investigates various physical properties of a black hole in the modified general relativity of f(R) gravity, aiming to constrain the values of different parameters. The behavior of particles and photon frequency shift are analyzed to determine the similarity between the studied black hole and astrophysical black holes in general relativity. The findings are crucial for the understanding of gravity.
Article
Astronomy & Astrophysics
G. G. L. Nashed, A. T. Shafeek
Summary: In this study, we derive non-flat cosmological models using Moller's tetradic theory of gravitation and investigate the effects of parameters on the models. We show the impact of non-extensive thermodynamics on the evolution of the universe.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Astronomy & Astrophysics
Z. Yousaf, G. G. L. Nashed, M. Z. Bhatti, H. Asad
Summary: The manuscript analyzes hyperbolically symmetric non-static fluid distribution with heat flux and electromagnetic field, constructing a general framework to examine the dynamic regime of matter configuration leading to static spacetime. The presence of negative energy density in the mass function indicates significant quantum implications, and the transport equation reveals the thermodynamic attributes of the fluid.astrophysico objects, Additionally, quasi-homologous constraint is used to construct various models, and valuable applications of astrophysical objects are deduced through evaluating analytical solutions in terms of kinematical variables.
Article
Astronomy & Astrophysics
Gamal Gergess Lamee Nashed
Summary: In this paper, we investigate the spherically symmetric black hole solution of the charged field equation in Rastall gravitational theory. We find that this solution is not affected by the Rastall parameter in the linear case, but when applied to a special form of nonlinear electrodynamics source, a novel solution involving the Rastall parameter is derived. This solution corresponds to the Anti-de-Sitter Reissner-Nordstrom spacetime and coincides with the Reissner-Nordstrom solution when the Rastall parameter vanishes.
Article
Physics, Multidisciplinary
G. G. L. Nashed, S. Nojiri
Summary: In this study, we construct spherically symmetric and static solutions in F(R) gravity coupled with electromagnetic fields. The solutions include new types of black holes with electric and magnetic charges. Our findings show that the higher-derivative terms in F(R) gravity make the curvature singularity softer compared to the charged black holes in Einstein's general relativity. We also calculate thermodynamical quantities of the obtained black holes and confirm the satisfaction of the first law of thermodynamics. Additionally, stability analysis reveals the existence of stable black hole solutions and indicates that the radial speed of the parity-odd mode is the speed of light.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2023)
Article
Astronomy & Astrophysics
G. G. L. Nashed
Summary: In this study, modified gravity field equations are applied to millisecond pulsars to examine the matter-geometry coupling and its effects on the star's properties. The explicit forms of the energy-momentum tensor components are derived, and it is shown that the matter-geometry coupling leads to smaller sizes for stars with the same mass under Einstein's general relativity. The hypothesis is validated by observations from additional pulsars.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
G. G. L. Nashed, A. Sheykhi
Summary: We present two new classes of analytical solutions in the framework of f (R) gravity. These solutions describe non-rotating and rotating black holes, respectively, and have non-trivial values of the Ricci scalar. The obtained solutions exhibit strong singularities in spacetime, indicating a change in the causal structure caused by the higher-order derivative terms in f (R) gravity.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Particles & Fields
G. G. L. Nashed
Summary: The equivalence between Rastall's theory of gravity and Einstein's general relativity theory is investigated by applying Rastall's theory to a spacetime with spherical symmetry. Assumptions are made about the form of the metric potential's temporal component and constraints are imposed to eliminate anisotropy, resulting in an isotropic spacetime. The study focuses on obtaining parameters that align with the behavior of pulsars and suggests that Rastall's parameter can play a crucial role in forming realistic compact objects consistent with observational data.
Article
Physics, Particles & Fields
G. G. L. Nashed
Summary: The mimetic gravitational theory has gained attention in cosmology and astrophysics. In this study, it is shown that an isotropic model cannot be derived in the frame of mimetic gravitation theory, leading to the exploration of the theory coupled with a Lagrangian multiplier. The field equations of a static isotropic gravitational system are studied and a new isotropic model is derived, providing consistent results with a realistic isotropic star.
Article
Astronomy & Astrophysics
G. G. L. Nashed
Summary: In this study, a new charged spherically symmetric black hole solution is derived by applying the Gauss-Bonnet equation of motions coupled with the scalar field and potential. The form of the scalar field, the function of the scalar, and the Gauss-Bonnet term are determined successfully. Additional terms, O(r16) and O(r19), are found in this black hole solution compared to the Riessner Nordstrom solution, which are responsible for reproducing the multi-horizon black hole solution. The modified first law of thermodynamics and the corresponding Smarr relation are derived due to the existence of these additional terms.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Particles & Fields
G. G. L. Nashed
Summary: By analyzing observational data from the pulsar PSR J0740+6620, researchers determined the parameter beta in the modified theory of general relativity and used it to model the physical quantities associated with the mass and radius of the pulsar. The results show that, compared to the predictions of general relativity, the modified theory predicts slightly larger sizes for neutron stars.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
G. G. L. Nashed, S. Capozziello
Summary: This study investigates the possible modifications of general relativity at ultraviolet and infrared scales, particularly considering the possibility of parity violation in strong gravity regime. The Chern-Simons gravity theory is used to account for the parity violation. The study shows that for certain spacetime structures, Chern-Simons gravity is equivalent to general relativity, but it is not applicable to (A)dS-Kerr/Kerr black holes. The thermodynamic quantities and geodesic equation of the black hole are also calculated.
Article
Astronomy & Astrophysics
G. G. L. Nashed
Summary: By utilizing the field equations of the modified teleparallel equivalent of general relativity, an exact solution for a static charged black hole in n-dimensions is obtained without imposing any constraints. The solution reveals distinctive dimensional constants associated with mass and electric charge, and the presence of electric charge leads to deviations from the predictions of teleparallel equivalent of general relativity. The study also investigates the thermodynamic properties of the black hole and shows its thermal stability.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Multidisciplinary Sciences
Gamal G. L. Nashed, Sergei D. Odintsov, Vasillis K. Oikonomou
Summary: Using the Gauss-Bonnet gravity framework, this study derives a new internal spherically symmetric solution with specific metric potentials and determines the values of constants based on observational data. The results show stability and satisfactory agreement with observational data.