Status of particle physics solutions to the UHECR puzzle
  The status of solutions to the ultra-high energy cosmic ray puzzle that involve particle physics beyond the standard model is reviewed. Signatures and experimental constraints are discussed for most proposals like the Z burst model and topological defects (both allowed only as subdominant contribution), supermassive dark matter (no positive evidence from its key signatures galactic anisotropy and photon dominance), strongly interacting neutrinos or new primaries (no viable models known), and violation of Lorentz invariance (possible). 
M. Kachelriess