Browsing by Author "Rubab Manzoor"

Now showing 1 - 5 of 5
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    Dynamics of axial symmetric system in self-interacting brans–dicke gravity.
    (European Physics Journal , Springer link, 2016) Rubab Manzoor
    This paper investigates dynamics of axial reflection symmetric model in self-interacting Brans-Dicke gravity for anisotropic fluid. We formulate hydrodynamical equations and discuss oscillations using time-dependent perturbation for both spin as well as spin-independent cases. The expressions of frequency, total energy density and equation of motion of oscillating model are obtained. We study instability of oscillating models in weak approximations. It is found that the oscillations and stability of the model depend upon the dark energy source along with anisotropy and reflection effects. We conclude that the axial reflection system remains stable for stiffness parameter Γ = 1, collapses for Γ > 1 and becomes unstable for 0 < Γ < 1.
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    Hydrodynamics of a gaseous system in massive brans-dicke gravity
    (The European Physical Journal Plus, Springer Link, 2016) Rubab Manzoor
    This paper explores hydrodynamics and hydrostatic of a star in the post-Newtonian approximation of massive Brans-Dicke gravity. We study approximated solutions of the field equations up to O(c−4) and generalize Euler equations of motion. We then formulate equations governing the stability and instability of the system. Finally, we discuss spherically symmetric stars for a specific barotropic case like dust, cosmic string and domain wall in this scenario.
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    Instability analysis of a cylindrical stellar object in brans–dicke gravity.
    (Journal of Experimental and Theoretical Physics, Springer Link, 2016) Rubab Manzoor
    This paper investigates instability ranges of a cylindrically symmetric collapsing cosmic filamentary structure in Brans-Dicke theory of gravity. For this purpose, we use perturbation approach in the modified field equations as well as dynamical equations and construct a collapse equation. The collapse equation with adiabatic index (Γ) is used to explore the instability ranges of both isotropic as well as anisotropic fluid in Newtonian and post-Newtonian approximations. It turns out that the instability ranges depend on the dynamical variables of collapsing filaments. We conclude that the system always remains unstable for 0 < Γ < 1 while Γ > 1 provides instability only for the special case.
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    Lemaitre-tolman-bondi dust cloud collapse in brans-dicke gravity
    (Modern Physics Letters A, 2014) Muhammad Sharif; Rubab Manzoor
    This paper investigates the phenomenon of gravitational collapse of Lemaitre–Tolman- Bondi (LTB) model in the presence of Brans–Dicke (BD) scalar field with nonzero potential field. We find a class of solutions by taking perfect fluid as well as scalar field and check the validity of weak energy conditions. It turns out that two different types of singularities are formed in the presence of scalar field. We conclude that the end state of gravitational collapse turns out to be a black hole (BH) contrary to general relativity (GR).
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    Structure scalars and anisotropic spheres in Brans-Dicke gravity
    (Physical Review D, 2015) M. Sharif; Rubab Manzoor
    This paper investigates self-gravitating spherically symmetric fluid models in Brans-Dicke gravity by incorporating structure scalars. We obtain ten scalar quantities using orthogonal splitting of the Reimann tensor and write down the set of governing equations in terms of these scalars. We determine inhomogeneity factors and conclude that inhomogeneity is a necessary condition for the resultant fluid models. Finally, we explore static inhomogeneous anisotropic spherical solutions with the help of these structure scalars.