GOLDSTINO DECOUPLING IN SPONTANEOUSLY BROKEN SUPERGRAVITY THEORIES

If the gravitino is sufficiently light and stable it will behave as an effective massless neutrino species at the time of nucleosynthesis. D epending on the temperature at which it decouples from the thermal bat h in the early universe, the gravitino mass will be bounded by the pri mordial He-4 abundance, Assuming a conservative estimate that the numb er of neutrino families, N-nu < 3.6, superlight gravitinos with a mass m(3/2) less than or similar to 10(-6) eV are ruled out, This bound is weaker than previous estimates because the Goldstino annihilation cro ss section was overestimated.