Browsing by Author "Sunzu, J. M."

Now showing 1 - 12 of 12
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    Charged anisotropic fluid spheres with conformal symmetry
    (Springer, 2023) Jape, J. W.; Maharaj, S. D.; Sunzu, J. M.; Mkenyeleye, J. M.
    We generate charged anisotropic exact models to the Einstein–Maxwell field equations for static spacetime with a conformal Killing vector. The Einstein–Maxwell field equations are solved to generate a realistic stellar model with physical significance. The generated model satisfies important physical requirements. The interior and exterior metrics match smoothly at the stellar surface, the surface red shift and the compactification parameter are within the suggested limits, regularity is obeyed, the energy conditions are satisfied, the sphere is stable, and the natural physical forces are balanced. The class of exact solutions generated in our model regains several models found by various researchers in the past. These include the models of Buchdahl, Vaidya and Tikekar, Durgapal and Bannerji, amongst other well-known solutions. The existence of a conformal Killing vector provides a geometric basis for many astrophysical objects.
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    Charged anisotropic models for quark stars
    (Springer, 2014) Sunzu, J. M.; Maharaj, S. D.; Ray, S.
    We perform a detailed physical analysis for a class of exact solutions for the Einstein-Maxwell equations. The linear equation of state consistent with quark stars has been incorporated in the model. The physical analysis of the exact solutions is performed by considering the charged anisotropic stars for the particular nonsingular exact model obtained by Maharaj, Sunzu and Ray. In performing such an analysis we regain masses obtained by previous researchers for isotropic and anisotropic matter. It is also indicated that other masses and radii may be generated which are in acceptable ranges consistent with observed values of stellar objects. A study of the mass-radius relation indicates the effect of the electromagnetic field and anisotropy on the mass of the relativistic star
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    Charged conformal stars and equation of state
    (Springer, 2023) Jape, J. W .; Sunzu, J. M.; Maharaj, S. D.; Mkenyeleye, J. M.
    Charged anisotropic fluid spheres admitting a conformal Killing vector with a linear equation of state are generated. Our approach incorporates a conformal symmetry and an equation of state to obtain the electric field intensity. The choice for one of the gravitational potentials from the conformal Killing relation is made on physical grounds to generate realistic stellar models with astrophysical significance. Several solutions generated in the past are contained in our generalized class of exact solution. The exact solutions satisfy several important physical conditions. The matching of the interior and exterior metrics is done smoothly at the stellar boundary. The mass, surface red shift, and compactness factor are compatible with observations. The stability requirement is obeyed, and the physical forces balance for equilibrium. The regularity condition is also satisfied.
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    Finite element numerical investigation into unsteady MHD radiating and reacting mixed convection past an impulsively started oscillating plate
    (MultiCraft, 2020) Reddy, Prabhakar B.; Matao, P. M.; Sunzu, J. M.
    In this article, numerical investigation is carried out for the unsteady MHD mixed convection flow of radiating and chemically reacting fluid past an impulsively started oscillating vertical plate with variable temperature and constant mass diffusion. The transport model employed includes the Hall current. A uniform magnetic field is applied transversely to the direction of the fluid flow. The flow consideration is subject to small magnetic Reynolds number. The Rosseland approximation is used to describe the radiation heat flux in the energy equation. The dimensionless governing system of partial differential equations of the flow has been solved numerically by employing the FEM. The influence of pertinent parameters on primary velocity, secondary velocity, temperature and concentration are presented graphically whereas primary skin friction, secondary skin friction, Nusselt number and Sherwood number are presented in tabular form. The findings of the present study are in good agreement with the earlier reported studies.
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    Finite element numerical investigation into unsteady MHD radiating and reacting mixed convection past an impulsively started oscillating plate
    (MultiCraft, 2020) Matao, P. M.; Reddy, B. Prabhakar; Sunzu, J. M.; Makinde, O. D.
    In this article, numerical investigation is carried out for the unsteady MHD mixed convection flow of radiating and chemically reacting fluid past an impulsively started oscillating vertical plate with variable temperature and constant mass diffusion. The transport model employed includes the Hall current. A uniform magnetic field is applied transversely to the direction of the fluid flow. The flow consideration is subject to small magnetic Reynolds number. The Rosse land approximation is used to describe the radiation heat flux in the energy equation. The dimensionless governing system of partial differential equations of the flow has been solved numerically by employing the finite element method. The influence of pertinent parameters on primary velocity, secondary velocity, temperature and concentration are presented graphically whereas primary skin friction, secondary skin friction, Nusselt number and Sherwood number are presented in tabular form. A comparison of the present method was made with the exact solution obtained by Rajput and Kanaujia (2016) by considering primary and secondary skin frictions, it was noticed that a very good agreement.
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    Generalized compact star models with conformal symmetry
    (Springer, 2021) Maharaj, S. D.; Sunzu, J. M.; Mkenyeleye, J. M.; Jape, J. M.
    We generate a new generalized regular charged anisotropic exact model that admits conformal symmetry in static spherically symmetric spacetime. Our model was examined for physical acceptability as realistic stellar models. The regularity is not violated, the energy conditions are satisfied, the physical forces balanced at equilibrium, the stability is satisfied via adiabatic index, and the surface red shift and mass–radius ratio are within the required bounds. Our conformal charged anisotropic exact solution contains models generated by Finch–Skea, Vaidya–Tikekar and Schwarzschild. Also, some recent charged or neutral and anisotropic or isotropic conformally symmetric models are found as special cases of our exact model. Our approach sing a conformal symmetry provides a generalized geometric framework for studying compact objects.
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    New exact models for anisotropic matter with electric field
    (Springer, 2017) Sunzu, J. M.; Danford, P.
    We generate two new exact models for the Einstein–Maxwell field equations. In our models, we consider the stellar object that is anisotropic and charged with linear equation of state consistent with quark stars. We have a new choice of measure of anisotropy that is physically reasonable. It is interesting that in our models we regain previous isotropic results as special cases. Isotropic exact solutions regained include models by Komathiraj and Maharaj; Mak and Harko; and Misner and Zapolsky. We can also obtain particular anisotropic models obtained by Maharaj, Sunzu, and Ray. The exact solutions corresponding to our models are found explicitly in terms of elementary functions. The graphical plots generated for the matter variables and the electric field are well behaved. We also generate relativistic stellar masses consistent with observations.
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    New models for quark stars with charge and anisotropy
    (2014) Sunzu, J. M.
    We find new classes of exact solutions for the Einstein-Maxwell field equations. The solutions are obtained by considering charged anisotropic matter with a linear equation of state consistent with quark stars. The field equations are integrated by specifying forms for the measure of anisotropy and one of the gravitational potentials which are physically reasonable. A general feature of our models is that isotropic pressures are regained when certain parameters vanish; this behaviour is missing in most previous treatments. Particular models found in our results generalize the models of Mak and Harko, Komathiraj and Maharaj, Misner and Zapolsky, and the earlier results of Einstein. The graphical and physical analyses indicate that the gravitational potentials, the matter variables, the electric field and the mass are well behaved. In performing physical analysis we regain masses and radii of stellar objects consistent with observations. It is also shown that other masses and radii may be generated which are in acceptable ranges consistent with observed values of stellar objects. In particular we have established that our model is consistent with the stellar object SAXJ1808.4-3658. A study of the mass-radius relation indicates the effect of the electromagnetic field and anisotropy on the mass of the relativistic star.
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    New stellar models generated using a quadratic equation of state
    (2018) Sunzu, J. M.; Thomas, M.
    We obtain new regular exact solutions to the field equations for uncharged relativistic stellar objects with vanishing pressure anisotropy. We assume a quadratic equation of state and a choice of measure of anisotropy and a metric function defining one of the gravitational potentials. In our exact models, we regain anisotropic and isotropic results generated by other researchers as a special case. It is interesting that our results are in agreement with Minkowski space–time and earlier Einstein models. The physical analysis of the plots reveals that the gravitational potentials and matter variables are well behaved in the stellar interior. Using our model, we generate finite relativistic stellar masses which are consistent with the astronomical objects previously found by other researchers.
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    Quark star model with charged anisotropic matter
    (Springer, 2014) Sunzu, J. M.; Maharaj., S. D.; Ray, S.
    We find two new classes of exact solutions to the Einstein-Maxwell system of equations. The matter distribution satisfies a linear equation of state consistent with quark matter. The field equations are integrated by specifying forms for the measure of anisotropy and a gravitational potential which are physically reasonable. The first class has a constant potential and is regular in the stellar interior. It contains the familiar Einstein model as a limiting case and we can generate finite masses for the star. The second class has a variable potential and singularity at the center. A graphical analysis indicates that the matter variables are well behaved.
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    Some simple models for quark stars
    (Springer, 2014) Maharaj, S. D.; Sunzu, J. M.; Ray, S.
    We find two new classes of exact solutions for the Einstein-Maxwell equations. The solutions are obtained by considering charged anisotropic matter with a linear equation of state consistent with quark stars. The field equations are integrated by specifying forms for the measure of anisotropy and a gravitational potential which are physically reasonable. The solutions found generalize the Mark-Harko model and the Komathiraj-Maharaj model. A graphical analysis indicates that the matter variables are well behaved.
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    Stellar models with generalized pressure anisotropy
    (Springer, 2019) Sunzu, J. M.; Mathias, A. K.; Maharaj, S. D.
    New models for a charged anisotropic star in general relativity are found. We consider a linear equation of state consistent with a strange quark star. In our models a new form of measure of anisotropy is formulated; our choice is a generalization of other pressure anisotropies found in the past by other researchers. Our results generalize quark star models obtained from the Einstein–Maxwell equations. Well-known particular charged models are also regained. We indicate that relativistic stellar masses for several stars are obtained using the general mass function found in our model.