Article
Astronomy & Astrophysics
Artur Alho, Jose Natario, Paolo Pani, Guilherme Raposo
Summary: This paper introduces a rigorous and general framework to study self-gravitating elastic materials within general relativity, and applies it to investigate the existence and viability of spherically symmetric elastic stars. The results show that elasticity contributes to increasing the maximum mass and compactness of the models, supporting the existence of compact stars with mass well above two solar masses.
Article
Astronomy & Astrophysics
V. S. Manko, E. Ruiz
Summary: In this paper, two physically meaningful configurations of a pair of equal Kerr-Newman corotating black holes separated by a massless strut are elaborated using the general equatorially symmetric two-soliton solution. The thermodynamic properties of these binary configurations are studied and the first law of thermodynamics taking correctly into account the magnetic field contribution is formulated for each case.
Article
Physics, Multidisciplinary
H. Alrebdi, Abdelghani Errehymy, Ksh Newton Singh, G. Mustafa, Abdel-Haleem Abdel-Aty, Mohammed Daoud
Summary: This article introduces a self-bound quark star model with net electric charge and compares it to four compact stars. The models satisfy various conditions and predict the radii of the compact objects.
Article
Physics, Particles & Fields
Marco Astorino, Adriano Vigano
Summary: In this paper, we study multi-black hole systems immersed in external gravitational field configurations in four-dimensional General Relativity. By using an infinite multipolar expansion, the conical singularities of a series of collinear static black holes are regularized. We also achieve a stationary rotating black hole system by adding independent angular momenta and NUT parameters to each source of the binary configuration. Furthermore, a charged extension of the binary black hole system at equilibrium is generated. Lastly, we demonstrate the consistent recovery of the binary Majumdar-Papapetrou solution in the vanishing external field limit.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
A. Bokulic, I Smolic, T. Juric
Summary: This study rederives the first law of black hole mechanics in the presence of nonlinear electrodynamics fields and discusses the validity of energy conditions, complementary proofs of the zeroth law of black hole electrodynamics, and aspects of the recently generalized Smarr formula, including its (non-)linearity and relation to the first law.
Article
Astronomy & Astrophysics
Gerard Clement, Dmitri Galtsov
Summary: In the framework of Einstein-Maxwell theory, we consider collinear arrays of rotating electrically charged black holes connected by Misner-Dirac strings. The first law of mechanics for these systems is derived, and the variations under different conditions are discussed.
Article
Physics, Particles & Fields
Omar Rodriguez-Tzompantzi
Summary: In this paper, we investigate the canonical structure of Exotic General Massive Gravity and discover a complete set of physical constraints using the Dirac Hamiltonian formalism. We also calculate the Poisson bracket algebra between these constraints and demonstrate that the theory is ghost-free under certain configurations, exhibiting only two physical degrees of freedom corresponding to one massive graviton. Additionally, we identify the transformation laws of the dynamical variables generated by the first-class constraints, which correspond to gauge symmetries.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Renan B. Magalhaes, Luis C. B. Crispino, Gonzalo J. Olmo
Summary: We study the correspondence between the solutions of general relativity (GR) and Ricci-based gravity theories (RBGs) of the f(R, Q) type. By focusing on the case of scalar matter, we establish the correspondence between the two theories for arbitrary f(R, Q) Lagrangian, with simplifications that arise when considering a free massless scalar in the GR frame. Using a spherically symmetric, static solution as a seed, we generate new compact objects in the target theory and find two types of solutions: one representing naked singularities and another corresponding to asymmetric wormholes with bounded curvature scalars everywhere, although the latter solutions are geodesically incomplete.
Article
Astronomy & Astrophysics
Alexandre Toubiana, Stanislav Babak, Enrico Barausse, Luis Lehner
Summary: Exotic compact objects can be difficult to distinguish from black holes in the inspiral phase of binaries observed by gravitational-wave detectors, but significant differences may be present in the merger and post-merger signal. A toy model capturing the key features of binaries of exotic compact objects with low compactness was introduced to assess their detectability and distinguishability from black hole binaries. The study showed that current detectors like LISA could potentially observe exotic binaries and differentiate them from black hole binaries.
Article
Astronomy & Astrophysics
Yves Brihaye, Betti Hartmann
Summary: We studied charged and rotating boson stars in five-dimensional Einstein-Maxwell-Chern-Simons theory, assuming equal angular momenta associated with the two orthogonal planes of rotation. In addition to the angular momenta, the boson stars also carry an electric charge and a magnetic moment. Interestingly, we discovered new branches of solutions for which the spatial part of the gauge potential has nodes, resulting in opposite signs for the magnetic moment and the gyromagnetic ratio compared to the solutions on the main branch. For sufficiently large energy density, the solutions exhibit ergoregions.
Article
Physics, Particles & Fields
Robert S. Bogadi, Megandhren Govender, Sibusiso Moyo
Summary: This study investigates the forces involved during the collapse of a compact stellar object and emphasizes the connection between fundamental quantities (forces) and the spacetime geometry in the gravitational formalism.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Aya Iyonaga, Tsutomu Kobayashi
Summary: We studied spatially covariant modified gravity where the scalar degree of freedom is rendered non-dynamical, resulting in two tensorial degrees of freedom, equivalent to general relativity. Analysis is done on how modified gravity theories with two tensorial degrees of freedom can be distinguished from general relativity observationally. The study confirms that this modified gravity theory predictions match general relativity for key parameters and does not affect asymptotically flat black holes. Additionally, by manipulating time-dependent functions, the cosmological dynamics can be made similar to the ΛCDM model.
Article
Materials Science, Multidisciplinary
Sachin Kumar, Divya Jyoti, Kottakkaran Sooppy Nisar, M. Zakarya
Summary: The Bonnor field offers insights into the imposition of two magnetic poles in a symmetric axis, with mass m and strengths -m and m. New exact solutions of Einstein-Maxwell field equations in pure magnetic fields under the Bonnor metric have been obtained using the Lie symmetry method, showcasing accelerating static solutions on a semi-Riemannian manifold that is not conformally flat. Additionally, graphical representations in 3D are provided.
RESULTS IN PHYSICS
(2021)
Article
Physics, Multidisciplinary
Fredrick W. Cotton
Summary: The proposed modifications to the Einstein-Maxwell equations include adding a scalar term and a four-dimensional nonlinear electromagnetic constitutive tensor, introducing additional curvature terms and a non-isotropic pressure tensor. These modifications allow for coupling between particle solutions, localized electromagnetic and gravitational wave solutions, and differentiate between Schwarzschild mass and inertial mass.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Physics, Particles & Fields
Zdenek Stuchlik, Jan Hladik, Jaroslav Vrba, Camilo Posada
Summary: Study investigates neutrino trapping in extremely compact Tolman VII objects, suggesting higher trapping efficiency compared to internal Schwarzschild spacetimes. Results indicate potential impact of neutrino trapping on neutron star cooling.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Multidisciplinary
Arkopriya Mallick, Indrani Karar, Farook Rahaman, Ritabrata Biswas
INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS
(2016)
Article
Physics, Multidisciplinary
S. O. Gladkov, A. Yadav, Saibal Ray, F. Rahaman
INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS
(2016)
Article
Physics, Multidisciplinary
Safiqul Islam, Shantanu Basu
CHINESE PHYSICS LETTERS
(2018)
Article
Physics, Multidisciplinary
F. Rahaman, S. Chakraborty, Saibal Ray, A. A. Usmani, S. Islam
INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS
(2015)
Article
Physics, Multidisciplinary
Safiqul Islam, Satadal Datta, Tapas K. Das
PRAMANA-JOURNAL OF PHYSICS
(2019)
Article
Astronomy & Astrophysics
G. S. Khadekar, Praveen Kumar, Safiqul Islam
JOURNAL OF ASTROPHYSICS AND ASTRONOMY
(2019)
Article
Computer Science, Hardware & Architecture
Runa Barik, Michael Welzl, Ahmed Elmokashfi, Thomas Dreibholz, Safiqul Islam, Stein Gjessing
PERFORMANCE EVALUATION
(2019)
Article
Physics, Nuclear
Nayan Sarkar, Susmita Sarkar, Farook Rahaman, Safiqul Islam
Summary: This study searches for new spherically symmetric wormhole solutions of the Einstein field equations based on the Karmarkar condition, obtaining corresponding solutions under three different redshift functions, with WH1 and WH2 violating the strong energy condition while WH3 does not, showcasing the presence of exotic matter within the wormholes.
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2021)
Article
Mathematics, Applied
Safiqul Islam, Muhammad Aamir, Irina Radinschi, Dwiptendra Bandyopadhyay
Summary: This research is an extension of previously published (2+1) dimensional cosmological models in f(R,T) gravity with lambda(R,T). A different class of cosmological space model, called lambda(R,T) gravity, is studied under modified theories of f(R,T) gravity, where the cosmological constant lambda is expressed as a function of the Ricci scalar R and the trace of the stress-energy momentum tensor T. The research focuses on finding a combined model that satisfies the equation of state for dark energy matter, quintessence matter, or perfect matter fluid. The study examines the energy conditions, pressure, and density in different cases and also analyzes the effective mass function and gravitational redshift function. The behavior of the cosmological constant is separately examined in the presence of different types of matter.
Proceedings Paper
Computer Science, Hardware & Architecture
Michael Welzl, Safiqul Islam, Runa Barik, Stein Gjessing, Ahmed Elmokashfi
2019 INTERNATIONAL CONFERENCE ON COMPUTING, NETWORKING AND COMMUNICATIONS (ICNC)
(2019)
Proceedings Paper
Computer Science, Hardware & Architecture
Satiqul Islam, Michael Welzl, Stein Gjessing
2019 INTERNATIONAL CONFERENCE ON COMPUTING, NETWORKING AND COMMUNICATIONS (ICNC)
(2019)
Proceedings Paper
Engineering, Electrical & Electronic
Safiqul Islam, Michael Welzl, Kristian Hiorth, David Hayes, Grenville Armitage, Stein Gjessing
IEEE INFOCOM 2018 - IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (INFOCOM WKSHPS)
(2018)
Proceedings Paper
Automation & Control Systems
Safiqul Islam, Michael Welzl, Stein Gjessing, Jianjie You
PROCEEDINGS OF 2016 IEEE ADVANCED INFORMATION MANAGEMENT, COMMUNICATES, ELECTRONIC AND AUTOMATION CONTROL CONFERENCE (IMCEC 2016)
(2016)
Proceedings Paper
Computer Science, Hardware & Architecture
Safiqul Islam, Michael Welzl, David Hayes, Stein Gjessing
NOMS 2016 - 2016 IEEE/IFIP NETWORK OPERATIONS AND MANAGEMENT SYMPOSIUM
(2016)
Proceedings Paper
Computer Science, Hardware & Architecture
Safiqul Islam, Michael Welzi
PROCEEDINGS OF THE ACM, IRTF & ISOC APPLIED NETWORKING RESEARCH WORKSHOP (ANRW'16)
(2016)
