Ultra High Energy Particles Propagation and the Transition from Galactic   to Extra-Galactic Cosmic Rays
  We discuss the basic features of the propagation of Ultra High Energy Cosmic Rays in astrophysical backgrounds, comparing two alternative computation schemes to compute the expected fluxes. We also discuss the issue of the transition among galactic and extra-galactic cosmic rays using theoretical results on fluxes to compare different models. 
Roberto Aloisio
astro-ph.HE hep-ph