Superheavy dark matter - art. no. 023501.

We show that in large-field inflationary scenarios, superheavy (many orders of magnitude larger than the weak scale) dark matter will be produced in c osmologically interesting quantities if superheavy stable particles exist i n the mass spectrum. We show that these particles may be produced naturally during the transition from the inflationary phase to either a matter-domin ated or radiation-dominated phase as a result of the expansion of the backg round spacetime acting on vacuum quantum fluctuations of the dark matter fi eld. We find that as long as there are stable particles whose mass is of th e order of the inflaton mass (presumably around 10(13) GeV), they will be p roduced in sufficient abundance to give Ohm(0) = 1, quite independently of any details of the nongravitational interactions of the dark-matter field. [S0556-2821(98)03124-5].