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Phantom Accretion onto the Schwarzschild de-Sitter Black Hole

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Chinese Physics Letters 2011年第9期28卷 34-37页

作者： m sharif G Abbas Department of mathematics University of the PunjabQuaid-e-Azam CampusLahore-54590Pakistan

We deal with phantom energy accretion onto the Schwarzschild de-Sitter black *** energy flux conservation,relativistic Bernoulli equation and mass flux conservation equation are formulated to discuss the phantom *** discuss the conditions for critical *** is found that the mass of the black hole decreases due to phantom *** exist two critical points which lie in the exterior of horizons(black hole and cosmological horizons).The results for the phantom energy accretion onto the Schwarzschild black hole can be recovered by takingΛ→0.

关键词： accretion horizon black

Symmetries of Energy-momentum Tensor： Some Basic Facts

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Communications in Theoretical Physics 2007年第5期47卷 829-834页

作者： m.sharif TariqIsmaeel Department of mathematics University of the PunjabQuaid-e-Azam CampusLahore-54590Pakistan

It has been pointed out by Hall et al. [Gen. Rel. Gray. 28 （1996） 299.] that matter collineations can be defined by using three different methods. But there arises the question whether one studies matter collineations by using LεTab=0, or LεT^ab = 0 or LεT^b a=0. These alternative conditions are, of. course, not generally equivalent. This problem has been explored by applying these three definitions to general static spherically symmetric spacetimes. We compare the results with each definition.

关键词： symmetries energy-momentum tensor

Anisotropic extensions of isotropic Finch–Skea metric in the charged modified gravity

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Communications in Theoretical Physics 2024年第9期76卷 118-140页

作者： Tayyab Naseer m sharif Department of mathematics and Statistics The University of Lahore1-Km Defence RoadLahore 54000Pakistan

In this study,we explore the Finch–Skea perfect fluid solution and extend its domain to three distinct anisotropic interior models within the framework of the f(R,T)theory,incorporating the influence of an electromagnetic *** assume a static spherical spacetime initially coupled with an isotropic matter *** then introduce a Lagrangian corresponding to an additional gravitating source,taking into account its role in inducing pressure anisotropy within the original fluid *** deriving the field equations for the combined matter setup,we applied a radial component transformation,which yielded two distinct systems of *** addition,we consider a charged exterior spacetime to determine the three constants associated with the Finch–Skea solution at the *** findings suggest that under certain parametric choices,all three resulting models exhibited physical relevance within this modified theory.

关键词： anisotropy modified gravity gravitational decoupling

Static Axially Symmetric models and Structure Scalars in Self-Interacting Brans–Dicke Gravity

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Communications in Theoretical Physics 2017年第7期67卷 39-48页

作者： m. sharif Rubab manzoor Department of mathematics University of the Punjab Quaid-e-Azam Campus Lahore-54590 Pakistan Department of mathematics University of Management and Technology Johar Town Campus Lahore-54782 Pakistan

This paper investigates static axially symmetric models in self-interacting Brans-Dicke gravity. We discuss physically feasible sources of models, derive field equations as well as evolution equations from Bianchi identities and construct structure scalars. Using these scalars and evolution equations, the inhomogeneity factors of the system are evaluated. It is found that structure scalars related to double dual of Riemann tensor control the density inhomogeneity. Finally, we obtain exact solutions of homogenous isotropic and inhomogeneous anisotropic spheroid models. It turns out that homogenous solutions reduce to Schwarzschild type interior solutions for a spherical case. We conclude that homogenous models involve homogenous distribution of scalar field whereas inhomogeneous correspond to inhomogeneous sca/ar field.

关键词： self-interacting Brans Dicke Theory self-gravitating systems structure scalars Non-sphericalsources interior solutions

Tidal Forces in Dyonic Reissner-Nrdstrom Black Hole

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Communications in Theoretical Physics 2018年第3期69卷 257-262页

作者： m.sharif Lubna Kousar Department of mathematics University of the Punjab Quaid-e-Azam Campus Lahore-54590 Pakistan

This paper investigates the tidal as well as magnetic charge effects produced in dyonic Reissner-Nordstroom black *** evaluate Newtonian radial acceleration using radial geodesics for freely falling test *** establish system of equations governing radial and angular tidal forces using geodesic deviation equation and discuss their solutions for bodies falling freely towards this black *** radial tidal force turns out to be compressing outside the event horizon whereas the angular tidal force changes sign between event and Cauchy horizons unlike Schwarzschild black *** radial geodesic component starts decreasing in dyonic Reissner-Nordstroom black hole unlike Schwarzschild *** conclude that magnetic charge strongly affects the radial as well as angular components of tidal force.

关键词： dyonic black hole tidal forces geodesics

Reconstruction of Scalar Field Dark Energy models in Kaluza-Klein Universe

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Communications in Theoretical Physics 2013年第8期60卷 183-188页

作者： m.sharif Abdul Jawad Department of mathematics University of the PunjabQuaid-e-Azam CampusLahore-54590Pakistan

This paper is devoted to study the modified holographic dark energy model by taking its different aspects in the t/at Kaiuza-Klein universe. We construct the equation of state parameter which evolutes the universe from quintessence region towards the vacuum. It is found that the modified holographic model exhibits instability against small perturbations in the early epoch of the universe but becomes stable in the later times. We also develop its correspondence with some scalar field dark energy models. It is interesting to mention here that ail the results are consistent with the present observations.

关键词： Kaluza-Klein cosmology modified holographic dark energy scalar field models

Evolution of Dissipative Anisotropic Expansion-Free Axial Fluids

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Communications in Theoretical Physics 2015年第8期64卷 139-144页

作者： m.sharif Zunaira Nasir Department of mathematics University of the Punjab Quaid-i-Azam Campus

A general study of non-static restricted class of axial system with anisotropic dissipative expansion-free fluid under geodesic condition is carried out. It is found that expansion-free model must be dissipative under geodesic condition to preserve axial symmetry. We also investigate this system without geodesic condition. Finally, the role of dissipation is explored via transport equation.

关键词： general relativity dissipative systems analytical

Viscosity Effects on Anisotropic Universe in Curvature-matter Coupling Gravity

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Communications in Theoretical Physics 2018年第5期69卷 537-543页

作者： m.sharif Aisha Siddiqa Department of mathematics University of the PunjabQuaid-e-Azam Campus

In this paper, we study evolution of the universe in the background of f(R, T) gravity using LRS Bianchi type-Ⅰ model. We discuss scale factors as well as deceleration parameter in dark energy dominated era for different bulk viscosity models. The occurrence of big-rip singularity is also examined. It is concluded that expansion is faster when bulk viscosity is proportional to Hubble parameter as compared to other models.

关键词： f(R T) gravity anisotropic universe bulk viscosity

Teleparallel Killing Vectors of Spherically Symmetric Spacetimes

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Communications in Theoretical Physics 2009年第9期52卷 435-440页

作者： m.sharif Bushra majeed Department of mathematics University of the Punjab

In this paper, Killing vectors of spherically spacetimes have been evaluated in the context of teleparallel theory of gravitation. Further, we investigate the Killing vectors of the Friedmann metrics. It is found that for static spherically spacetimes the number of Killing vectors turns out to be seven while for the Friedmann models, we obtain six teleparallel Killing vectors. The results are then compared with those of General Relativity. We conclude that both of these descriptions of gravity do not provide the consistent results in general. However, these results may coincide under certain conditions for a particular spacetime.

关键词： teleparallel theory Killing vectors