title: Violation of the Greisen-Zatsepin-Kuzmin cutoff: a tempest in a (magnetic) Teapot? Why cosmic ray energies above 10(20) eV may not require new physics.
abstract: The apparent lack of suitable astrophysical sources for the observed highest energy cosmic rays within approximately 20 Mpc is the "Greisen-Zatsepin-Kuzmin (GZK) paradox." We constrain representative models of the extragalactic magnetic field structure by Faraday rotation measurements; limits are at the microG level rather than the nG level usually assumed. In such fields, even the highest energy cosmic rays experience large deflections. This allows nearby active galactic nuclei (possibly quiet today) or gamma ray bursts to be the source of ultrahigh energy cosmic rays without contradicting the GZK distance limit.
authors.affiliation: Department of Physics, New York University, New York, New York 10003, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Farrar
authors.forename: T
authors.initials: T
authors.lastname: Piran
mesh_terms: D001256:Astronomy / Q000379:methods; D003359:Cosmic Radiation; D008962:Models, Theoretical; D010825:Physics / Q000379:methods