TOPOLOGICAL DEFECTS AND HIGHEST ENERGY COSMIC AND GAMMA RAYS

In this paper we review the hypothesis that a considerable part of the cosmic ray flux observed above about ${10}^{19}\text{eV}$ may be produced by decaying or annihilating topological defects left over from phase transitions in the early universe at grand unification energy scales ($\approx {10}^{16}\text{GeV}$). Possible signatures of cosmic ray producing defect models are discussed which could be tested experimentally in the near future. We thereby focus on model independent universal spectral properties of the predicted particle fluxes.