Approaching Space Time Through Velocity in Doubly Special Relativity
  We discuss the definition of velocity as dE/dp, where E,p are the energy and momentum of a particle, in Doubly Special Relativity (DSR). If this definition matches dx/dt appropriate for the space-time sector, then space-time can in principle be built consistently with the existence of an invariant length scale. We show that, within different possible velocity definitions, a space-time compatible with momentum-space DSR principles can not be derived. 
R. Aloisio, A. Galante, A.F. Grillo, E. Luzio and F. Mendez