Classical and Quantum Analysis of Repulsive Singularities in Four   Dimensional Extended Supergravity
  Non--minimal repulsive singularities (``repulsons'') in extended supergravity theories are investigated. The short distance antigravity properties of the repulsons are tested at the classical and the quantum level by a scalar test--particle. Using a partial wave expansion it is shown that the particle gets totally reflected at the origin. A high frequency incoming particle undergoes a phase shift of $\frac{\pi}{2}$. However, the phase shift for a low--frequency particle depends upon the physical data of the repulson. The curvature singularity at a finite distance $r_h$ turns out to be transparent for the scalar test--particle and the coordinate singularity at the origin serves as a repulsive barrier at which particles bounce off. 
I. Gaida, H. R. Hollmann, J. M. Stewart (Cambridge U., DAMTP)