The gravitino abundance in supersymmetric `new' inflation models

We consider the abundance of gravitinos created from the vacuum fluctuation, in a class of `new' inflation models for which global supersymmetry is a good approximation. Immediately after inflation, gravitinos are produced, with number density determined by equations recently presented by Kallosh et. al. (hep-th/9907124) and Giudice et. al. (hep-ph/9907510). Unless reheating intervenes, creation may continue, maintaining about the same number density, until the Hubble parameter falls below the gravitino mass. In any case, the abundance of gravitinos created from the vacuum fluctuation exceeds the abundance from thermal collisions in a significant regime of parameter space, leading to tighter cosmological constraints.Comment: 9 pages latex. Same results but argument for late-time creation now appears in hep-ph/991231

Models of inflation and their predictions

Taking field theory seriously, inflation model-building is difficult but not impossible. The observed value of the spectral index of the adiabatic density perturbation is starting to discriminate between models, and may well pick out a unique one in the forseeable future.Comment: Latex 5 pages. To appear in Particle Physics and the Early Universe (COSMO99), AIP (1999

Can the curvaton paradigm accommodate a low inflation scale?

The cosmological curvature perturbation may be generated when some `curvaton' field, different from the inflaton, oscillates in a background of unperturbed radiation. In its simplest form the curvaton paradigm requires the Hubble parameter during inflation to be bigger than 10^7\GeV, but this bound may be evaded if the curvaton field (or an associated tachyon) is strongly coupled to a field which acquires a large value at the end of inflation. As a result the curvaton paradigm might be useful in improving the viability of low-scale inflation models, in which the supersymmetry-breaking mechanism is the same as the one which operates in the vacuum.Comment: 8 pages. This version will appear in PLB, contains another inequality with no essential change in the conclusio