We study the production of gravitinos during the preheating era after inflation by means of the non-perturbative Bogolyubov technique. Considering only the helicity $\pm 3/2$ states, the problem is reduced to the simpler Dirac fermions case. We calculate the production in a particular supergravity model in an expanding universe and obtain the spectrum and number density. Finally we compare the results with the nucleosynthesis bounds and extract some consequences.
Categories: hep-ph astro-ph hep-th