Can the curvaton paradigm accommodate a low inflation scale?

TL;DR

The paper examines whether the curvaton mechanism can salvage very low-scale inflation by generating the observed curvature perturbation after inflation. It shows that in the simplest curvaton model, the inflationary Hubble scale must satisfy $H_* > 10^7$ GeV, which challenges low-scale scenarios. By considering variants—a heavy curvaton, evolving curvaton dynamics, and PNGB/tachyonic mass effects—the work identifies dynamical channels that can relax or modify this bound, though each comes with caveats such as non-Gaussianity constraints or tight model requirements. Overall, the study clarifies when curvaton dynamics can align with low-scale inflation and highlights concrete mechanisms that could enable viable, low-scale SUSY-breaking-inspired cosmologies.

Abstract

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.