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Search Results: 1 - 10 of 144650 matches for " F. Rahaman "
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Non static Global monopole in Lyra geometry
F. Rahaman,R. Mondal
Physics , 2007,
Abstract: A class of non static solutions around a global monopole resulting from the breaking of a global S0(3) symmetry based on Lyra geometry are obtained. The solutions are obtained using the functional separability of the metric coefficients. We have shown that the monopole exerts attractive gravitational effects on test particles.
Static global monopoles in higher dimensional space time
R. Mukherjee,F. Rahaman
Physics , 2007,
Abstract: We present an exact solution around global monopole resulting from the breaking of a global S0(3) symmetry in a five dimensional space time. We have shown that the global monopole in higher dimensional space time exerts gravitational force which is attractive in nature. It is also shown that the space around global monopole has a deficit solid angle. Finally, we study monopole in higher dimensional space time within the framework of Lyra geometry.
Semiclassical gravitational effects around global monopole in Brans-Dicke theory
F. Rahaman,P. Ghosh
Physics , 2008, DOI: 10.1142/S0217732308026546
Abstract: In recent past, W.A.Hiscock [ Class.Quan.Grav. (1990) 7,6235 ] studied the semi classical gravitational effects around global monopole. He obtained the vacuum expectation value of the stress-energy tensor of an arbitrary collection of conformal mass less free quantum fields (scalar, spinor and vectors) in the space time of a global monopole. With this stress-energy tensor, we study the semi classical gravitational effects of a global monopole in the context of Brans-Dicke theory of gravity.
Gravitational field of domain wall in Lyra geometry
F. Rahaman,P. Ghosh
Physics , 2008, DOI: 10.1007/s10509-008-9866-8
Abstract: In this paper, we study the domain wall with time dependent displacement vectors based on Lyra geometry in normal gauge i.e. displacement vector $f^*_i = [ \beta (t), 0,0,0]$. The field theoretic energy momentum tensor is considered with zero pressure perpendicular to the wall. We find an exact solutions of Einstein equation for a scalar field $\phi$ with a potential $V(\phi)$ describing the gravitational field of a plane symmetric domain wall. We have seen that the hyper surfaces parallel to the wall ($ z = constant $) are three dimensional de-sitter spaces. It is also shown that the gravitational field experienced by test particle is attractive.
Thin-shell wormholes from black holes with dilaton and monopole fields
F. Rahaman,A. Banerjee
Physics , 2011, DOI: 10.1007/s10773-011-0965-x
Abstract: We provide a new type of thin-shell wormhole from the black holes with dilaton and monopole fields. The dilaton and monopole that built the black holes may supply fuel to construct the wormholes. Several characteristics of this thin-shell wormhole have been discussed. Finally, we discuss the stability of the thin-shell wormholes with a "phantom-like" equation of state for the exotic matter at the throat.
Gravitational field of higher dimensional domain walls in Lyra geometry
F. Rahaman,S. Mandal
Physics , 2006,
Abstract: This paper studies Thick domain wall within the framework of Lyra geometry. Their exact solutions are obtained in the background of a five dimensional space-time. The space-time is nonsingular in its both spatial and temporal behavior. The gravitational field of the wall is shown to be attractive in nature.
New Class of Magnetized Inhomogeneous Bianchi Type-I Cosmological Model with Variable Magnetic Permeability in Lyra Geometry
Ahmad T Ali,F Rahaman
Physics , 2013, DOI: 10.1007/s10773-013-1719-8
Abstract: Inhomogeneous Bianchi type-I cosmological model with electro-magnetic field based on Lyra geometry is investigated. Using separated method, the Einstein field equations have been solved analytically with the aid of Mathematica programm. A new class of exact solutions have been obtained by considering the potentials of metric and displacement field are functions of coordinates t and x. We have assumed that F(12) is the only non-vanishing component of electro-magnetic field tensor F(ij). The Maxwells equations show that F(12) is the function of x alone whereas the magnetic permeability is the function of x and t both. To get the deterministic solution, it has been assumed that the expansion scaler Theta in the model is proportional to the value sigma(11) of the shear tensor sigma(ij). Some physical and geometric properties of the model are also discussed and graphed.
Simultaneous emergence of curved spacetime and quantum mechanics
S S De,F Rahaman
Physics , 2014, DOI: 10.1139/cjp-2015-0454
Abstract: It is shown in this paper that the geometrically structureless spacetime manifold is converted instantaneously to a curved one, the Riemannian or may be a Finslerian spacetime with an associated Riemannian spacetime, on the appearance of quantum Weyl spinors dependent only on time in that background flat manifold and having the sympleic property in the abstract space of spinors. The scenario depicts simultaneous emergence of the gravity in accord with general relativity and quantum mechanics.The emergent gravity leads to the generalized uncertainty principle, which in turn, ushers in discrete space time. The emerged space time is specified here as to be Finslerian and the field equation in that space time has been obtained from the classical one due to the arising quantized space and time. From this field equation we find the quantum field equation for highly massive (of the Planck order) spinors in the associated Riemannian space of the Finsler space, which is in fact, the background FRW space time of the universe.These highly massive spinors provide the mass distribution complying Einstein equivalence principle. All these occurred in the indivisible minimum time considered as zero time or spontaneity.
Energy Distribution for Non-commutative Radiating Schwarzschild Black Holes
I. Radinschi,F. Rahaman,U. F. Mondal
Physics , 2012, DOI: 10.1007/s10773-012-1304-6
Abstract: The aim of this article is the calculation of the energy-momentum for a non-commutative radiating Schwarzschild black hole in order to obtain the expressions for energy. We make the calculations with the Einstein and M\oller prescriptions. We show that the expressions for energy in both the prescriptions depend on the mass $M$, $\theta$ parameter and radial coordinate. We make some comparisons between the results. Our results show that the Einstein prescription is a more powerful concept than the M\oller prescription.
Can electro-magnetic field, anisotropic source and varying $Λ$ be sufficient to produce wormhole spacetime ?
F. Rahaman,M. Kalam,K. A. Rahman
Physics , 2008, DOI: 10.1007/s10773-009-9936-x
Abstract: It is well known that solutions of general relativity which allow for traversable wormholes require the existence of exotic matter (matter that violates weak or null energy conditions [WEC or NEC]). In this article, we provide a class of exact solution for Einstein-Maxwell field equations describing wormholes assuming the erstwhile cosmological term $\Lambda$ to be space variable, viz., $\Lambda = \Lambda (r)$. The source considered here not only a matter entirely but a sum of matters i.e. anisotropic matter distribution, electromagnetic field and cosmological constant whose effective parts obey all energy conditions out side the wormhole throat. Here violation of energy conditions can be compensated by varying cosmological constant. The important feature of this article is that one can get wormhole structure, at least theoretically, comprising with physically acceptable matters.
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