The cosmological moduli problem and preheating

Many models of supersymmetry breaking, in the context of either supergravit y or superstring theories, predict the presence of particles with Planck-su ppressed couplings and masses around the weak scale. These particles are ge nerically called moduli. The excessive production of moduli in the early Un iverse jeopardizes the successful predictions of nucleosynthesis. In this p aper we show that the efficient generation of these dangerous relics is an unescapable consequence of a wide variety of inflationary models which have a preheating stage. Moduli are generated by a current in a novel way which differs from the usual production mechanism during parametric resonance. T he corresponding limits on the reheating temperature are often very tight a nd more severe than the bound of 10(9) GeV coming from the production of mo duli via thermal scatterings during reheating.