Curvaton scenario with low scale inflation revisited

In its simplest form the curvaton paradigm requires the Hubble parameter during inflation to be bigger than $10^8 \GeV$, but this bound may be evaded in non-standard settings. In the heavy curvaton scenario the curvaton mass increases significantly after the end of inflation. We reanalyze the bound in this set up, taking into account the upper bound on the curvaton mass from direct decay. We obtain $H_* > 10^8 \GeV$ if the mass increase occurs at the end of inflation, and $H_* > 10^{-14} \GeV$ if it occurs just before nucleosynthesis. We then discuss two implementations of the heavy curvaton. Parameters are constrained in these explicit models, and as a result even obtaining TeV scale inflation is no small feat