Gravitino production during preheating

We study the production of gravitinos during the preheating era after infla tion by means of the non-perturbative Bogolyubov technique. Considering onl y the helicity +/-3/2 states, the problem is reduced to the simpler Dirac f ermions case. We calculate the production in a particular supergravity mode l in an expanding universe and obtain the spectrum and number density. Fina lly we compare the results with the nucleosynthesis bounds and extract some consequences.