• K S Govinder

      Articles written in Pramana – Journal of Physics

    • A charged spherically symmetric solution

      K Moodley S D Maharaj K S Govinder

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      We find a solution of the Einstein-Maxwell system of field equations for a class of accelerating, expanding and shearing spherically symmetric metrics. This solution depends on a particularansatz for the line element. The radial behaviour of the solution is fully specified while the temporal behaviour is given in terms of a quadrature. By setting the charge contribution to zero we regain an (uncharged) perfect fluid solution found previously with the equation of statep = μ + constant, which is a generalisation of a stiff equation of state. Our class of charged shearing solutions is characterised geometrically by a conformal Killing vector.

    • An analysis of the nonlinear equation $u_t = f(x, u)u_{xx} + g(x, u)u^2_x + h(x, u)u_x + p(x, u)$

      R M Edelstein K S Govinder

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      We use the method of preliminary group classification to analyse a particular form of the nonlinear diffusion equation in which the inhomogeneity is quadratic in $u_x$. The method yields an optimal system of one-dimensional subalgebras. As a result we obtain those explicit forms of the unknown functions 𝑓, 𝑔, ℎ and 𝑝 for which the equation admits additional point symmetries.

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