  A scenario for gravitational particle creation in a stiff matter dominated
flat Friedmann-Robertson-Walker universe is presented. The primary creation of
scalar particles is calculated using quantum field theory in curved spacetime
and it is found to be strongly dependent on the scalar mass and the expansion
parameter of the universe. The particle creation is most effective for a very
massive scalar field and large expansion parameter. We apply the results to
cosmology and calculate an upper bound for the equilibrium temperature of the
secondary particles created by the scalar field decay.
