Master Dissertations

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Browsing Master Dissertations by Subject "Anisotropic"

Now showing 1 - 3 of 3
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    Generalized exact anisotropic neutral star model with embedding approach
    (The University of Dodoma, 2022) Pastory, Makalo
    Using embedding approach, this study presents exact solutions to the Einstein field equations for anisotropic neutral stars in more generalized form. The study involves a generalization of the choice of metric potential made by Mathias, Maharaj, Sunzu and Mkenyeleye in which the choice of metric potential is in more specific form. Under embedding approach, one of the metric potentials is chosen on physical grounds while the Karmarkar condition is used to generate the second metric potential. Modelled masses and radii in acceptable ranges for neutral stars are found. Moreover, masses and radii consistent with stars like LMCX-4, Her X-1, cen X-3, 4U 1538-52, vela X-1, and SAX J1808.4-3658 are also generated.
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    Models for an isotropic stellar objects with no electric field.
    (The University of Dodoma, 2016) Lighuda, Avirt Simon
    In this dissertation, we generate solutions to Einstein-Maxwell field equations devoted to neutral anisotropic stellar objects using linear equation of state. The field equations are transformed by adopting Bannerji and Durgapal transformation. We generated the solutions to Einstein field equations and obtain matter variables and gravitational potentials by using the general differential equation governing the model. In our model isotropic results are regained as a special case. The plotted graphs and physical analysis show that matter variables and the gravitational potentials are all well behaved. That is, energy density, radial pressure, tangential pressure and gravitational potentials are finite, regular and continuous everywhere inside the stellar objects.
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    Realistic relativistic stellar anisotropic models with equation of state
    (The University of Dodoma, 2017) Thomas, Mashiku
    We obtain new exact solutions to the Einstein field equations for anisotropic neutral stellar objects. In our dissertation, we are considering a quadratic equation of state and a choice of measure of anisotropy and metric function adopted from Sunzu’s work. We transform the Einstein field equations for neutral anisotropic matter by adopting the Durgapal and Bannerji’s new variables. We generate the exact solution and hence obtain the gravitational potentials and matter variables from the general differential equation of the model. In our models, we regain the previous anisotropic and isotropic results generated by Sunzu as a special case. It is interesting that our results agree with Minkowski spacetime and earlier Einstein model. The physical analysis of the plots reveals that gravitational potentials and matter variables are well behaved in the interior of the stellar objects. In our model, we generate finite masses which are consistent with astronomical objects found by other researchers.