A pedestrian approach to the high energy limits of branes and other   gravitational systems
  In this article we study limits of models that contain a dimensionful parameter such as the mass of the relativistic point-particle. The limits are analogous to the massless limit of the particle and may be thought of as high energy limits. We present the ideas and work through several examples in a (hopefully) pedagogical manner. Along the way we derive several new results. 
Ulf Lindstrom and Harald Svendsen