Ultrahigh Energy Cosmic Rays: Old Physics or New Physics?
/ Authors
/ Abstract
We consider the advantages of and the problems associated with hypotheses to explain the origin of ultrahigh energy cosmic rays (UHECR: E > 10 EeV) and the “trans-GZK” cosmic rays (TGZK: E > 100 EeV) both through “old physics” (acceleration in cosmic sources) and “new physics” (new particles, topological defects, fat neutrino cross sections, Lorentz invariance violation).