Article
Astronomy & Astrophysics
Adolfo Cisterna, Anibal Neira-Gallegos, Julio Oliva, Scarlett C. Rebolledo-Caceres
Summary: The study demonstrates that the Plebanski-Demianski spacetime remains a solution of general relativity when supplemented with both a conformally coupled scalar theory and quadratic curvature corrections. The research also involves obtaining new hairy black hole solutions and analytically extending specific metric spacetimes to produce healthy asymptotically AdS wormhole configurations.
Article
Physics, Multidisciplinary
Byron P. Brassel, Sunil D. Maharaj, Rituparno Goswami
Summary: The study examines energy conditions for higher-dimensional Hawking-Ellis Type I and Type II matter fields in a relativistic astrophysical context, analyzing an inhomogeneous composite fluid distribution with anisotropy, shear stresses, non-vanishing viscosity, null dust, and null string energy density. The presence of the higher dimension N is explicitly considered in a system of six equations, with the geometry of the (N - 2)-sphere influencing the form and structure of the energy conditions. Additionally, energy conditions for higher-dimensional Type II fluid are derived, showing a recovery of Type I fluid conditions under certain restrictions, and encompassing all previous treatments for four dimensions.
PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS
(2021)
Article
Physics, Particles & Fields
Sunil D. Maharaj, Byron P. Brassel
Summary: This paper examines the junction conditions for a generalized matter distribution in a radiating star, involving internal composite distribution of barotropic matter, null dust, and a null string fluid in shear-free spherical spacetime, and external distribution of radiation field and a null string fluid. The study extends the familiar Santos result with barotropic matter to the boundary condition for the composite matter distribution at the stellar surface, and also considers the boundary condition for general spherical geometry in the presence of shear and anisotropy for a generalized matter distribution.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Multidisciplinary
Eric Kilgore
Summary: In this study, I investigate global, causal solutions to the spherically symmetric Einstein scalar field system. By introducing new bounds and constructing a particular set of generalized wave coordinates, I demonstrate the stability and existence of large data solutions.
ANNALES HENRI POINCARE
(2022)
Article
Astronomy & Astrophysics
Yasutaka Koga, Tomohiro Harada, Yuichiro Tada, Shuichiro Yokoyama, Chul-Moon Yoo
Summary: By incorporating the effect of critical phenomena of gravitational collapse, the study investigates the probability distribution of effective inspiral spin, mass ratio, and chirp mass of primordial black hole (PBH) binaries. It is found that although critical phenomena can lead to large spins on the low-mass tail, the effective inspiral spin of the binary is statistically very small, and there is almost no anticorrelation between effective inspiral spin and mass ratio.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Cheng-Yong Zhang, Qian Chen, Yunqi Liu, Wen-Kun Luo, Yu Tian, Bin Wang
Summary: In this study, we present the first fully nonlinear investigation on the accretion of scalar fields onto a seed black hole in anti-de Sitter spacetime in Einstein-Maxwell-scalar theory. We uncover intrinsic critical phenomena in the dynamical transition between bald and scalarized black holes. Additionally, we propose a new physical mechanism to dynamically descalarize an isolated scalarized black hole. Moreover, the first results on critical phenomena in descalarizations are revealed, distinguishing between discontinuous and continuous dynamical descalarizations based on the presence of an intermediate attractor.
Article
Astronomy & Astrophysics
Kimihiro Nomura, Daisuke Yoshida
Summary: This study investigates the general properties of universes without initial singularity, finding that the universal covering of a nonsingular universe must have the topology of S3 and the affine size of a nonsingular universe is bounded above.
Article
Astronomy & Astrophysics
Chul-Moon Yoo, Tomohiro Harada, Shin'ichi Hirano, Hirotada Okawa, Misao Sasaki
Summary: In this study, we numerically investigate the formation of primordial black holes (PBHs) caused by an isocurvature perturbation in the radiation-dominated Universe. Our simulations of spherically symmetric configurations show that a PBH is formed if the amplitude of the scalar field profile is sufficiently large. However, we find that the late-time behavior of the gravitational collapse is dominated by the dynamics of the fluid, rather than the scalar field.
Article
Astronomy & Astrophysics
Rajes Ghosh, Akash K. Mishra, Sudipta Sarkar
Summary: The study employs the weak cosmic censorship conjecture as a consistency criterion to investigate modified extremal black holes. The results indicate that in certain cases, the constraints on parameters are strong enough to reproduce the same bounds present in solutions obtained from independent research.
Article
Astronomy & Astrophysics
Filip Hejda, Jose P. S. Lemos, Oleg B. Zaslavskii
Summary: We revisit the unified version of the BSW effect concerning collisions of charged particles in a rotating electrovacuum black hole spacetime, and explain the origins of the seemingly incompatible limiting cases. We also demonstrate that there are no unconditional upper bounds on the extracted energy for arbitrarily small values of the black hole electric charge.
Article
Astronomy & Astrophysics
Stephon Alexander, Gregory Gabadadze, Leah Jenks, Nicolas Yunes
Summary: We studied the dynamical Chern-Simons gravity as an effective quantum field theory, and found that slowly rotating black holes acquire novel geometric structures due to the gravitational dynamical Chern-Simons term. The rotating black-hole solutions exhibit caplike domains with nonstandard dynamics within them, violating the focusing condition for geodesics. This implies that the Hawking-Penrose singularity theorem cannot be straightforwardly applied to probe matter within the Chern-Simons caps.
Article
Astronomy & Astrophysics
Johannes Munch
Summary: The causal structure of the recent loop quantum gravity black hole collapse model is analyzed, finding that the presence of a causal horizon in the eternal metric and the role of shock wave and spacetime discontinuity in the collapsing scenario. The study also explores the possibilities of continuous matter collapse with only timelike evolution and presents a solution with an infinite extended causal diagram. Through the analysis of radial light rays, causal diagrams of these spacetimes are sketched out.
Article
Astronomy & Astrophysics
Yu-Sen An, Li Li, Fu-Guo Yang
Summary: This study proves the absence of inner Cauchy horizons in general nonlinear electrodynamics black holes with charged scalar hairs, regardless of the form of scalar potential and nonlinear electrodynamics. It also shows that the null energy condition can rule out the existence of Cauchy horizons for hyperbolic black holes. The complex interior dynamics are closely related to the instability of the inner Cauchy horizon triggered by scalar hairs.
Article
Astronomy & Astrophysics
Patrick Bourg, Carsten Gundlach
Summary: Our numerical simulations of gravitational collapse in 2+1 spacetime dimensions with ultrarelativistic equation of state reveal type I and type II critical phenomena at different thresholds, showcasing static and non-self-similar contracting quasistatic solutions respectively.
Article
Astronomy & Astrophysics
Yisong Yang
Summary: We study the equations of motion for static dyonic matters using nonlinear electrodynamics of the Born-Infeld theory type. Exact finite-energy solutions are obtained in the quadratic and logarithmic nonlinearity cases, which lead to dyonically charged black holes with relegated curvature singularities. We demonstrate that the dyonic solutions restore electromagnetic symmetry and resolve a density-pressure inconsistency issue exhibited by the original Born-Infeld model.
Article
Physics, Mathematical
M. Z. Bhatti, Z. Yousaf, Z. Tariq
Summary: Employing the Palatini version of f(R) gravity theory, this paper describes the evolution of a radiating axially symmetric fluid and its changeover to a non-radiating state. The orthonormal tetrad formalism is used to evaluate the components of various tensors and structure scalars, yielding insights into the characteristics of the fluid source. Differential equations are worked out to gain insight into the consistency of modified field equations during the transition from radiating to equilibrium state.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Astronomy & Astrophysics
Z. Yousaf, M. Z. Bhatti, S. Rehman, Kazuharu Bamba
Summary: This study investigates the effects of magnetic fields in non-linear electrodynamics in chameleonic Brans-Dicke theory with the existence of anisotropic spherical fluid. Specifically, it explores dissipative and non-dissipative self-gravitating systems in the quasi-homologous regime under the minimal complexity constraint. Analytic solutions are found under these circumstances. Furthermore, the dynamics of a dissipative fluid is analyzed, demonstrating that a void covering the center can satisfy the Darmois criteria. The temperature of self-gravitating systems is also studied.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Astronomy & Astrophysics
M. Z. Bhatti, M. Yousaf, Z. Yousaf
Summary: This manuscript establishes the gravitational junction conditions for f (G, T) gravity, which is a gravitational theory where f is an arbitrary function of the Gauss-Bonnet invariant G and the trace of the energy-momentum tensor T. The study introduces the gravity theory and obtains a scalar-tensor representation with two scalar fields and scalar potential. The junction conditions for matching between two space-times on a separation hyper-surface are derived, and it is found that thin-shells are not allowed in this theory. The results hold in the scalar-tensor representation as well, emphasizing their equivalence. The study significantly constrains models for alternative compact structures supported by thin-shells in f (G, T) gravity and provides a framework for smooth matching at the surface.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Physics, Mathematical
Umber Sheikh, Yousra Aziz, M. Z. Bhatti, Richard Pincak
Summary: The aim of this study is to discuss the evolution of compact stars using a string fluid in Rastall theory and the Krori-Barua metric as the interior geometry. Matching the interior and exterior spacetimes leads to coefficients of the KB ansatz. The model is applied to specific physical features and it is found that the string fluid is responsible for the evolution of compact stars. The presented model fulfills all the physical requirements and is considered realistic.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Astronomy & Astrophysics
M. M. M. Nasir, M. Z. Bhatti, Z. Yousaf
Summary: Through this study, we provide a comprehensive summary of recent research on complexity factor (C-f) in the context of modified gravity theories (MGT). Particularly, we investigate the C-f of the novel MGT called f(G, T-2) gravity under the anisotropic static fluid configuration. We employ two mass approaches and a vanishing complexity condition to find solutions for the nonlinear system and explore two additional models for comprehensive results.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Article
Astronomy & Astrophysics
M. Z. Bhatti, Z. Yousaf, M. Nazir
Summary: This manuscript examines thin-shell wormholes in the framework of f(R,T) theory. By selecting an appropriate function, exact solutions for traversable wormholes are found and their stability is investigated.
Article
Astronomy & Astrophysics
Z. Yousaf, Ahmed M. Galal, M. Z. Bhatti, A. Farhat
Summary: This manuscript studies the inhomogeneity in the energy density for the relativistic dynamical charged system by considering the anisotropic distribution of radiating fluid and using the f(G, T-2) theory. The results show that modified terms and charge have a considerable impact on the fluid inhomogeneity in both non-radiating and radiating scenarios.
Article
Physics, Multidisciplinary
Z. Yousaf, M. Z. Bhatti, H. Aman, P. K. Sahoo
Summary: This work investigates the bouncing nature of the Universe using an isotropic configuration of fluid T-alpha beta and Friedmann-Lemaitre-Robertson-Walker metric scheme. The study is carried out under the novelf (g, T alpha beta T alpha beta ) gravitation and assumes a specific model. An analysis of the Hubble parameter and a graphical review of the bounce are provided. The conditions for a bouncing model are also checked.
Article
Multidisciplinary Sciences
Z. Yousaf, M. Z. Bhatti, U. Farwa
Summary: This article investigates the physical features of static axial sources that produce complexity within the matter configuration within the perspective of f (R, T) theory. The contracted Bianchi identities of effective and normal matter are used to develop the conservation equations. By splitting the curvature tensor to compute structure scalars, the physical aspects of the source are determined. The complexity of the system is calculated by exploring the evolving source and the corresponding propagation equations.
Article
Plant Sciences
Aamir Khan, Mohammad Safdar Baloch, Naimat Ullah, Sheikh Zain Ul Abidin, Muhammad Zeeshan Bhatti, Raees Khan, Asghar Ali Khan, Hammad Ismail, Asma Saeed, Hadia Gul
Summary: This study compared the performance of phosphate solubilizing bacteria (PSB) as bio-fertilizer with commercially available phosphate fertilizers on wheat crop. The results showed that the application of N2-fixing bacteria as PSB had the best effect.
PLANT SCIENCE TODAY
(2023)
Article
Mathematics, Applied
Z. Yousaf, M. Z. Bhatti, S. Khan, A. Malik, Haifa I. Alrebdi, Abdel-Haleem Abdel-Aty
Summary: This investigation explores the factors that generate pressure anisotropy in dynamical spherically symmetric stellar systems using the stringy-inspired Gauss-Bonnet modification of general relativity. By considering the modified form of Tolman-Oppenheimer-Volkoff for the quadratic-f(G) gravitational model, we analyze the hydrostatic equilibrium of self-gravitating systems. We formulate a differential equation based on the Weyl curvature scalar, also known as an evolution equation, to understand the evolution of stellar structure. Our findings suggest that fluid variables such as shear, heat flux, and irregular energy density caused by extra f(G)-terms in the fluid flow contribute to the anisotropy in initially isotropic stellar structures. The presented results are physically relevant and compatible with the classical model.
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, Multidisciplinary
Z. Yousaf, M. Z. Bhatti, H. Aman, Adnan Malik
Summary: Recently, Glavan and Lin proposed a novel gravitational scheme, 4D-EGB gravity, by rescaling the coupling factor a as a/ D-4 and developing the field equations. This paper aims to derive the cosmic bounce with a cubic form of scale factor and study the bouncing scenario under these assumptions. The flat FLRW metric and perfect fluid are used to examine the energy conditions, with different values of the coupling factor a and cosmological constant A. The assumed scale factor model demonstrates the stability of universal expansion and allows for the universal bounce by validating the energy conditions.
INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS
(2023)
Article
Physics, Multidisciplinary
Z. Yousaf, M. Z. Bhatti, A. Farhat
Summary: In this study, we analyze the distribution of self-gravitating collapsing fluid in a spherically symmetric spacetime by using modified Gauss-Bonnet gravity theory to identify the factors responsible for energy-density inhomogeneity. The modified Einstein's equations are used to observe the variations in the mass function due to different quantities. Dynamical equations and two differential equations for Weyl curvature are formulated and utilized to investigate the quantities that contribute to the inhomogeneity.
PRAMANA-JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
M. Z. Bhatti, Z. Yousaf, A. Rehman
Summary: This study analyzes the celestial object gravastar in the context of f(R, G) gravity, as an alternative to black holes. The stability of the gravastar model is evaluated using matching conditions and demonstrated with graphs. The role of f(R, G) theory in maintaining the sustainability of the model is also examined.
INDIAN JOURNAL OF PHYSICS
(2023)
