The cosmological moduli problem and preheating

Many models of supersymmetry breaking, in the context of either supergravityor superstring theories, predict the presence of particles withPlanck-suppressed couplings and masses around the weak scale. These particlesare generically called moduli. The excessive production of moduli in the earlyUniverse jeopardizes the successful predictions of nucleosynthesis. In thispaper we show that the efficient generation of these dangerous relics is anunescapable consequence of a wide variety of inflationary models which have apreheating stage. Moduli are generated as coherent states in a novel way whichdiffers from the usual production mechanism during parametric resonance. Thecorresponding limits on the reheating temperature are often very tight and moresevere than the bound of 10^9 GeV coming from the production of moduli viathermal scatterings during reheating.Comment: 17 pages, 5 Postscript figures, corrected some typo