Article
Physics, Particles & Fields
Isil Basaran Oz, Kazuharu Bamba
Summary: This paper investigates the f(R) theory in static cylindrically symmetric and plane-symmetric spacetimes. Solutions to the field equations of these models are found using the Noether symmetry method, leading to the discovery of new solutions. Additionally, the GR limit for each case is examined.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Materials Science, Multidisciplinary
Abu Bakr Mehmood, Fiaz Hussain, Ashfaque H. Bokhari, Muhammad Ramzan, Muhammad Faryad, Tahir Hussain
Summary: This article addresses the problem of finding non-static plane symmetric perfect fluid solutions in the f(R, T) theory of gravity. The authors propose a classification for such spacetimes and calculate solutions within each class, finding both static and non-static geometries. The authors also analyze the Killing symmetries to determine the Lie symmetry groups admitted by the obtained spacetimes, finding a range of Killing vector fields.
RESULTS IN PHYSICS
(2022)
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
Isil Basaran Oz, Kazuharu Bamba
Summary: The solutions for the field equations of f(R) gravity in static cylindrically symmetric space-time were investigated. Unknown values of the equations of state parameter were determined through the analysis of constraints obtained by using the Noether symmetry method. Several new exact solutions for cases of General Relativity in static cylindrically symmetrical space-time for the non-dust matter were discovered.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Multidisciplinary Sciences
Zinnat Hassan, Ghulam Mustafa, Pradyumn Kumar Sahoo
Summary: This article discusses the study of wormhole solutions in f(Q) gravity with noncommutative geometry, exploring linear and exponential models and confirming the physical capability and stability of the obtained solutions through graphical analysis and the Tolman-Oppenheimer-Volkov equation.
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
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, Particles & Fields
M. Z. Bhatti, S. Ijaz, Bander Almutairi, A. S. Khan
Summary: This paper analyzes the characteristics of a non-static sphere with an anisotropic fluid distribution in the background of modified f (G) theory. The presence of a conformal Killing vector allows for the computation of reliable results for the modified field equations. Various precise analytical solutions are obtained for both non-dissipative and dissipative systems by making different choices of the conformal Killing vector. The matching conditions in the context of f (G) gravity are computed and specific constraints are applied to determine significant results. The results of this study help in understanding the properties of astrophysical objects.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Julio C. Fabris, Ednaldo L. B. Junior, Manuel E. Rodrigues
Summary: This article investigates the implementation of black bounce solutions in f(R) theories. It is found that violation of the energy conditions still occurs in these solutions, albeit less severe than in General Relativity (GR) cases. The authors propose a zero-density model with horizons and present a model with positive energy density, which differs from GR.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Multidisciplinary
Raja Solanki, Zinnat Hassan, P. K. Sahoo
Summary: In this work, we explore wormhole geometries in the framework of ������ (������, ������������) gravity. We derive field equations for the generic ������(������, ������������) function using the static and spherically symmetric Morris-Thorne wormhole metric. Two non-linear ������(������, ������������) models are considered, namely ������(������, ������������) = ������2 + ������������������and ������ (������, ������������) = ������2 + (1 + ������������)������������, where ������ and ������are free model parameters. By assuming three cases, we obtain wormhole solutions for linear barotropic, anisotropic, and isotropic equations of state. The violation of null energy condition and the use of exotic matter in wormhole throat are discussed, with the conclusion that modified gravity theories can provide stable traversable wormhole solutions.
CHINESE JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
Maria Shubina
Summary: In this paper, we investigate the metric power-law f(R) similar to Rn- gravity model for the four-dimensional metric tensor with two coordinates. We derive exact analytical vacuum solutions for various values of n, including both non-stationary configurations of the travelling wave type and stationary ones, particularly dependent on one radial variable.
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
Physics, Multidisciplinary
M. Sharif, Tayyab Naseer
Summary: This paper presents new exact solutions to the field equations in the context of f(R, T) gravity using minimal gravitational decoupling. Two sets of modified field equations are obtained by transforming the radial metric potential, with each set corresponding to a different source. Constraints are imposed on the additional source to make the second set solvable, and the unknowns are determined by smoothly matching the interior and exterior spacetimes. The physical viability and stability of the obtained solutions are analyzed using the mass and radius of a compact star 4U 1820 - 30.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Materials Science, Multidisciplinary
Avik De, Simran Arora, Uday Chand De, P. K. Sahoo
Summary: The article first investigates the geometrical structures of a pseudo-symmetric spacetime under the condition of conformal flatness, and then further studies the spacetime solutions of F(R)-gravity theory and their relationships with cosmological effects.
RESULTS IN PHYSICS
(2022)
Article
Physics, Mathematical
Mushtaq Ahmad, Muhammad Ramzan, Fiaz Hussain, Shabeela Malik
Summary: The main goal of this study is to investigate the Noether symmetries for a class of static plane symmetric solutions in f(T) gravity and extract conservation laws using these symmetries. It is found that this class of solutions admits 5, 6, 8, 9, 11, and 17 Noether symmetries in f(T) gravity.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Physics, Multidisciplinary
M. Farasat Shamir, Adnan Malik
CANADIAN JOURNAL OF PHYSICS
(2019)
Article
Astronomy & Astrophysics
Mushtaq Ahmad, M. Farasat Shamir
ASTROPHYSICS AND SPACE SCIENCE
(2019)
Article
Physics, Multidisciplinary
M. Farasat Shamir, Adnan Malik
COMMUNICATIONS IN THEORETICAL PHYSICS
(2019)
Article
Physics, Multidisciplinary
G. Mustafa, Xia Tie-Cheng, M. Farasat Shamir
Article
Astronomy & Astrophysics
M. Farasat Shamir, Tayyaba Naz
Article
Astronomy & Astrophysics
M. Farasat Shamir
Article
Astronomy & Astrophysics
G. Mustafa, Xia Tie-Cheng, Mushtaq Ahmad, M. Farasat Shamir
Summary: This article investigates compact anisotropic matter profiles in the context of f (R, T) gravity, utilizing spherical symmetric space-time and Karmarkar's condition. By considering Schwarzschild exterior solution and experimental statistics of three different stars, it concludes that all observed stars are realistic, stable, and free from singularities.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Physics, Multidisciplinary
G. Mustafa, Ibrar Hussain, M. Farasat Shamir, Xia Tie-Cheng
Summary: This study delves into the Rastall theory of modified gravity applied to three different compact stars, based on observational facts. By assuming the Karmarkar condition with an anisotropic fluid profile, the study uses an explicit g(rr) metric potential element to solve differential equations and explore essential physical attributes and parameters. The results obtained are considered to be significant and accurate, with graphically presented solutions feasible for the stellar objects in question. The implications of the Rastall parameter and its role in solutions satisfying the Karmarkar condition for anisotropic matter are also investigated, along with the exploration of dark stars within the framework of Rastall gravity.
Article
Astronomy & Astrophysics
M. Farasat Shamir
Summary: This study investigates bouncing cosmology in the context of f(G, T) theory of gravity, using a Gauss-Bonnet cosmological model with a logarithmic trace term. By considering two equations of state parameters, the possibility of obtaining bouncing solutions is explored, with graphical analysis showing promising results. The violation of energy conditions near bouncing points suggests an accelerating universe based on recent observational data.
ADVANCES IN ASTRONOMY
(2021)
Article
Astronomy & Astrophysics
M. Farasat Shamir
Summary: This paper investigates the oscillating universe in f(G, T) gravity through two Gauss-Bonnet cosmological models with logarithmic and linear trace terms, respectively. Bouncing solutions are explored and energy conditions are studied, indicating violations near bouncing points consistent with accelerating universe observations. Hubble and deceleration parameters behavior is examined, predicting initial and future bounces for both models. Analysis also focuses on conservation equation in modified gravity theories, suggesting the possibility of recovering the usual conservation equation of general relativity. Overall, f(G, T) gravity models provide good bouncing solutions in this study.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Physics, Multidisciplinary
Tayyaba Naz, Ammara Usman, M. Farasat Shamir
Summary: This study investigates a new classification of embedded class-I solutions of compact stars using the Karmarkar condition in f(R) gravity background. By considering different models of f(R) theory of gravity and conducting physical tests, the study confirms the viability of the models in describing the behavior of compact objects.
Article
Physics, Particles & Fields
M. Farasat Shamir, G. Mustafa, Mushtaq Ahmad
Summary: This manuscript investigates compact geometries using the Karmarkar condition with charged anisotropic source of matter distribution, focusing on the implication of the Bardeen model as an outer spacetime. The analysis includes profiles of pressure, energy density, charged density, anisotropy function, electric field attributes, energy bounds, red-shift function, compactness parameter, stability, and adiabatic index, showing that the obtained solutions are physically viable and stable.
Article
Physics, Multidisciplinary
G. Mustafa, Tie-Cheng Xia, M. Farasat Shamir
Summary: This study explores stellar structures in Rastall gravity using the embedding approach in spherically static symmetric space-time, investigating the connection conditions by calculating and matching exterior and interior solutions, analyzing multiple physical parameters and stability of stellar structures.
Article
Physics, Particles & Fields
M. Farasat Shamir, Ammara Usman, Tayyaba Naz
Summary: The study aims to explore relativistic configurations of compact object solutions using a specific gravity model, establishing field equations and analyzing physical characteristics. The Bardeen black hole model is found to accurately describe realistic stellar structures.
ADVANCES IN HIGH ENERGY PHYSICS
(2021)
Article
Physics, Multidisciplinary
M. Farasat Shamir, Zoya Asghar, Adrian Malik
Summary: This study investigates the behavior of compact stars in the background of f (R, T) theory of gravity and examines their physical behavior using an exponential gravity model. The results validate the existence of compact stars under this gravity model.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2022)
