Long range forces induced by neutrinos at finite temperature

We revisit and extend previous work on neutrino mediated long range forces in a backround at finite temperature. For Dirac neutrinos, we correct existing results. We also give new results concerning spin-dependent as well as spin-independent long range forces associated to Majorana neutrinos. An interesting outcome of the investigation is that, for both types of neutrinos whether massless or not, the effect of the relic neutrino heat bath is to convert those forces into attractive ones in the supra-millimeter scale while they stay repulsive within the sub-millimeter scale.Comment: 8 pages, Latex, 1 figur

Production of light pseudoscalars in external electromagnetic fields by the Schwinger mechanism

We generalize the Schwinger mechanism and calculate the probability of the decay of intense electromagnetic fields to pseudoscalar particles. We also point out that our estimate for axion emission in a previous paper was incorrect.Comment: 25 pages including 9 figures. Version that matches published versio

Astrophysical constraints on superlight gravitinos

I review the constraints on the mass of gravitinos that follow from considerations on energy loss in stars and from Big Bang Nucleosynthesis arguments.Comment: Invited talk at the 5th Workshop on High Energy Physics Phenomenology(WHEPP-5), Pune, India, 12-26 January 199

Gravitinos from Gravitational Collapse

We reanalyse the limits on the gravitino mass $m_{3/2}$ in superlight gravitino scenarios derived from arguments on energy-loss during gravitational collapse. We conclude that the mass range $10^{-6}eV\leq m_{3/2}\leq2.3\times10^{-5}eV$ is excluded by SN1987A data. In terms of the scale of supersymmetry breaking $\Lambda$, the range $70GeV\leq\Lambda \leq 300GeV$ is not allowed.Comment: 6 pages, latex, no figures. Numerical typo correcte