Generalised Functions and Distributional Curvature of Cosmic Strings
  A new method is presented for assigning distributional curvature, in an invariant manner, to a space-time of low differentiability, using the techniques of Colombeau's `new generalised functions'. The method is applied to show that curvature of a cone is equivalent to a delta function. The same is true under small enough perturbations. 
C J S Clarke, J A Vickers and J P Wilson (Department of Mathematics,   University of Southampton, Southampton, UK.)