期刊文献+
共找到7篇文章
< 1 >
每页显示 20 50 100
Thin-Shell Wormholes Admitting Conformal Motions in Spacetimes of Embedding Class One
1
作者 Peter K. F. Kuhfittig 《International Journal of Astronomy and Astrophysics》 2024年第3期162-171,共10页
This paper discusses the feasibility of thin-shell wormholes in spacetimes of embedding class one admitting a one-parameter group of conformal motions. It is shown that the surface energy density σis positive, while ... This paper discusses the feasibility of thin-shell wormholes in spacetimes of embedding class one admitting a one-parameter group of conformal motions. It is shown that the surface energy density σis positive, while the surface pressure is negative, resulting in , thereby signaling a violation of the null energy condition, a necessary condition for holding a wormhole open. For a Morris-Thorne wormhole, matter that violates the null energy condition is referred to as “exotic”. For the thin-shell wormholes in this paper, however, the violation has a physical explanation since it is a direct consequence of the embedding theory in conjunction with the assumption of conformal symmetry. These properties avoid the need to hypothesize the existence of the highly problematical exotic matter. 展开更多
关键词 Thin-Shell Wormholes Conformal Symmetry Embedding Class One Exotic Matter
下载PDF
A new class of viable and exact solutions of EFEs with Karmarkar conditions:an application to cold star modeling
2
作者 Neeraj Pant Megandhren Govender Satyanarayana Gedela 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第5期71-83,共13页
In this work we present a theoretical framework within Einstein’s classical general relativity which models stellar compact objects such as PSR J1614-2230 and SAX J1808.4-3658.The Einstein field equations are solved ... In this work we present a theoretical framework within Einstein’s classical general relativity which models stellar compact objects such as PSR J1614-2230 and SAX J1808.4-3658.The Einstein field equations are solved by assuming that the interior of the compact object is described by a class I spacetime.The so-called Karmarkar condition arising from this requirement is integrated to reduce the gravitational behaviour to a single generating function.By appealing to physics we adopt a form for the gravitational potential which is sufficiently robust to accurately describe compact objects.Our model satisfies all the requirements for physically realistic stellar structures. 展开更多
关键词 Compact star ANISOTROPY embedding class Einstein field equations adiabatic index
下载PDF
Periodic Signature Change in Spacetimes of Embedding Class One
3
作者 Peter K. F. Kuhfittig 《International Journal of Astronomy and Astrophysics》 2022年第2期167-176,共10页
The idea of an oscillating Universe has remained a topic of interest even after the discovery of dark energy. This paper confirms this idea by means of another well-established theory in general relativity, the embedd... The idea of an oscillating Universe has remained a topic of interest even after the discovery of dark energy. This paper confirms this idea by means of another well-established theory in general relativity, the embedding of curved spacetimes in higher-dimensional flat spacetimes: an n-dimensional Riemannian space is said to be of embedding class m if m +n is the lowest dimension of the flat space in which the given space can be embedded;here . So a four-dimensional Riemannian space is of class two and can therefore be embedded in a six-dimensional flat space. A line element of class two can be reduced to a line element of class one by a suitable coordinate transformation. The extra dimension can be either spacelike or timelike, leading to accelerating and decelerating expansions, respectively. Accordingly, it is proposed in this paper that the free parameter occurring in the transformation be a periodic function of time. The result is a mathematical model that can be interpreted as a periodic change in the signature of the embedding space. This signature change may be the best model for an oscillating Universe and complements various models proposed in the literature. 展开更多
关键词 Signature Change Oscillating Universe Embedding Class One
下载PDF
Relativistic models of anisotropic superdense star in the regime of Karmarkar's condition
4
作者 Bikram Keshari Parida Shreya Majumder +2 位作者 Shyam Das Koushik Chakraborty Farook Rahaman 《Communications in Theoretical Physics》 SCIE CAS CSCD 2023年第2期168-179,共12页
We obtained a new class of solutions for a relativistic anisotropic compact star by utilizing the Karmarkar embedding condition.To obtain the closed-form solution a suitable form of one of the gravitational potentials... We obtained a new class of solutions for a relativistic anisotropic compact star by utilizing the Karmarkar embedding condition.To obtain the closed-form solution a suitable form of one of the gravitational potentials has been chosen to determine the other by analyzing the Karmarkar condition.The resulting solutions are found to be well-behaved and regular and could describe a compact stellar object.Considering the current estimated values of the mass and radius of the pulsar 4U1820-30 as input parameters,all the physically relevant parameters are shown to be well-behaved to a very good degree of accuracy. 展开更多
关键词 anisotropic compact star embedding class one Karmarkar’s condition
原文传递
On the Spectrum of a Class of Differential Operators and Embedding Theorems 被引量:5
5
《Acta Mathematica Sinica,English Series》 SCIE CSCD 1994年第4期415-427,共13页
The author considers the embedding problem of weighted Sobolev spaces H<sup>n</sup><sub>p</sub> in weighted L<sub>s</sub> spaces L<sub>s,r</sub>,and some sufficient cond... The author considers the embedding problem of weighted Sobolev spaces H<sup>n</sup><sub>p</sub> in weighted L<sub>s</sub> spaces L<sub>s,r</sub>,and some sufficient conditions and necessary conditions are given, when weight functions satisfy certain conditions.The author uses the results obtained to the qualitative analysis of the spectrum of 2n-order weighted differential operator,and gives some sufficient conditions and necessary conditions to ensure that the spectrum is discrete. 展开更多
关键词 CL On the Spectrum of a Class of Differential Operators and Embedding Theorems 关户
原文传递
Anisotropic compact stars in Karmarkar spacetime
6
作者 Ksh.Newton Singh Neeraj Pant M.Govender 《Chinese Physics C》 SCIE CAS CSCD 2017年第1期131-138,共8页
We present a new class of solutions to the Einstein field equations for an anisotropic matter distribution in which the interior space-time obeys the Karmarkar condition. The necessary and sufficient condition require... We present a new class of solutions to the Einstein field equations for an anisotropic matter distribution in which the interior space-time obeys the Karmarkar condition. The necessary and sufficient condition required for a spherically symmetric space-time to be of Class One reduces the gravitational behavior of the model to a single metric function. By assuming a physically viable form for the grr metric potential we obtain an exact solution of the Einstein field equations which is free from any singularities and satisfies all the physical criteria. We use this solution to predict the masses and radii of well-known compact objects such as Cen X-3, PSR J0348+0432, PSR B0943+10and XTE J1739-285. 展开更多
关键词 general relativity exact solution embedding class I Karmarkar condition ANISOTROPY compact stars
原文传递
Anisotropic stars in modified gravity:An extended gravitational decoupling approach
7
作者 S.K.Maurya B.Mishra +1 位作者 Saibal Ray Riju Nag 《Chinese Physics C》 SCIE CAS CSCD 2022年第10期239-258,共20页
In this study,we conduct an investigation on decoupling gravitational sources under the framework of f(R,T)gravity.Basically,the complete geometric deformation technique is employed,which facilitates finding the exact... In this study,we conduct an investigation on decoupling gravitational sources under the framework of f(R,T)gravity.Basically,the complete geometric deformation technique is employed,which facilitates finding the exact solutions to the anisotropic astrophysical system smoothly without imposing any particular ansatz for the deformation function.In addition,we used 5-dimensional Euclidean spacetime in order to describe the embedding Class Ⅰ spacetime in order to obtain a solvable spherical physical system.The resulting solutions are both physically interesting and viable with new possibilities for investigation.Notably,the present investigation demonstrates that the mixture of f(R,T)+CGD translates to a scenario beyond the pure GR realm and helps to enhance the features of the interior astrophysical aspects of compact stellar objects.To determine the physical acceptability and stability of the stellar system based on the obtained solutions,we conducted a series of physical tests that satisfied all stability criteria,including the nonsingular nature of density and pressure. 展开更多
关键词 modified gravity embedding class I spacetime neutron stars
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部