Ultra-high-energy cosmic rays and inflation relies

There are two processes of matter creation after inflation that may be rele vant to the resolution of the puzzle of cosmic rays observed with energies beyond GZK cut-off: 1) gravitational creation of superheavy (quasi)stable p articles, and 2) non-thermal phase transitions leading to the formation of topological defects. We review both possibilities. (C) 1999 Elsevier Scienc e B.V. All rights reserved.