排序方式: 共有13条查询结果,搜索用时 703 毫秒
1.
Mehedi Kalam Farook Rahaman Sajahan Molla S. Monowar Hossein 《Astrophysics and Space Science》2014,349(2):865-871
We propose a relativistic model for: quintessence stars with the combination of an anisotropic pressure corresponding to normal matter and a quintessence dark energy having a characteristic parameter ω q such that $-1<\omega_{q}< -\frac{1}{3}$ . We discuss various physical features of the model and show that the model satisfies all the regularity conditions and can provide stable equilibrium configurations. 相似文献
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F. Rahaman M. Kalam A. DeBenedictis A. A. Usmani Saibal Ray 《Monthly notices of the Royal Astronomical Society》2008,389(1):27-33
In the present investigation, flat rotational curves of the galaxies are considered under the framework of brane-world models where the four-dimensional effective Einstein equation has extra terms which arise from the embedding of the 3-brane in the five-dimensional bulk. It has been shown here that these long-range bulk gravitational degrees of freedom can act as a mechanism to yield the observed galactic rotation curves without the need for dark matter. The present model has the advantage that the observed rotation curves result solely from well-established non-local effects of gravitation, such as dark radiation and dark pressure under a direct use of the condition of flat rotation curves and does not invoke any exotic matter field. 相似文献
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K. K. Nandi A. I. Filippov F. Rahaman Saibal Ray A. A. Usmani M. Kalam A. DeBenedictis 《Monthly notices of the Royal Astronomical Society》2009,399(4):2079-2087
Several aspects of the 4 d imprint of the 5 d bulk Weyl radiation are investigated within a recently proposed model solution. It is shown that the solution has a number of physically interesting properties. The constraints on the model imposed by combined measurements of rotation curve and lensing are discussed. A brief comparison with a well-known scalar field model is also given. 相似文献
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Farook Rahaman Mubasher Jamil Mehedi Kalam Kaushik Chakraborty Ashis Ghosh 《Astrophysics and Space Science》2010,325(1):137-147
We investigate the spacetime of anisotropic stars admitting conformal motion. The Einstein field equations are solved using
different ansatz of the surface tension. In this investigation, we study two cases in details with the anisotropy as: (1)
p
t
=n
p
r
, (2)
-p_r=(+c_2)p_{t}-p_{r}=\frac{1}{8\pi}(\frac{c_{1}}{r^{2}}+c_{2})
where, n, c
1 and c
2 are arbitrary constants. The solutions yield expressions of the physical quantities like pressure gradients and the mass. 相似文献
6.
In this article, we suggest a Sitter model in favor of compact stars in low-mass X-ray binaries.Here, we have considered the presence of a cosmological constant(on a small scale) to investigate the stellar structure. We conclude that this approach is very suitable for the familiar physical model of compact stars in low-mass X-ray binaries. We calculate the probable radius, compactness(u) and surface redshift(Z_s) of six compact stars in low-mass X-ray binaries, namely Cyg X-2, V395 Carinae/2 S 0921–630, XTE J2123–058,X1822–371(V691 CrA), 4 U 1820–30 and GR Mus(XB 1254–690). We also offer a possible equation of state(EOS) for the stellar objects. 相似文献
7.
It is known that for a thin domain wall the pressure in the perpendicular direction to the wall is negligible. In this paper,
we have evaluated solutions for thin domain walls with spherical symmetry following two different approaches. The exact solutions
are obtained using functional separability of the metric coefficients.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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This paper studies thin domain walls within the frame work of Lyra Geometry. We have considered two models. First one is the thin domain wall with negligible pressures perpendicular and transverse direction to the wall and secondly, we take a particular type of thin domain wall where the pressure in the perpendicular direction is negligible but transverse pressures are existed. It is shown that the thin domain walls have no particle horizon and the gravitational force due to them is attractive. 相似文献
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Few years ago, Cho and Vilenkin have proposed that topological defects can arise in symmetry breaking models without having degenerate vacua. These types of defects are known as vacuumless defects. In the present work, the gravitational field of a vacuumless global string and global monopole have been investigated in the context of Lyra geometry. We find the metric of the vacuumless global string and global monopole in the weak field approximations. It has been shown that the vacuumless global string can have repulsive whereas global monopole exerts attractive gravitational effects on a test particle. It is dissimilar to the case studied in general relativity. 相似文献
10.
Azad Md. Abul Kalam Islam Abu Reza Md. Towfiqul Ayen Kurratul Rahman Md. Siddiqur Shahid Shamsuddin Mallick Javed 《Theoretical and Applied Climatology》2022,148(3-4):1261-1278
Theoretical and Applied Climatology - Understanding changes in monsoon precipitation patterns is crucial as it determines the occurrence, intensity, and duration of floods and droughts in... 相似文献