Propagation of ultra high energy protons and gamma rays over cosmological distances and implications for topological defect models

Abstract We describe the results of a hybrid matrix-Monte Carlo calculation of cascading of UHE cosmic rays and γ -rays through the cosmic background radiation fields over cosmological distances. We calculate the γ -ray and neutrino emission that results from the cascade, as well as the effect of cascading on the primary spectrum. We discuss the results for various cosmic ray injection spectra and primary species. Certain models for the production of the highest energy cosmic rays are ruled out.