Extragalactic cosmic rays

Abstract

I review the status of ultrahigh-energy cosmic ray (UHECR) physics. After introducing the main experimental results and summarizing possible intepretations, I discuss observational and theoretical constraints on the sources of UHECRs. I comment also briefly on the role of magnetic fields. Combining these constraints, I argue that luminuous and numerous AGN types as FR-I and Seyfert galaxies, or alternatively hypernovae, are the most promising UHECR sources. Finally, I sketch few of the models presented at the conference before concluding. effect at high energies, we see a smaller and smaller fraction of the Universe for lower CR energies.