The curvaton as a Pseudo-Nambu-Goldstone boson, JHEP 0307 (2003) 053, [arXiv:hep-ph/0304050

The field responsible for the cosmological curvature perturbations generated during a stage of primordial inflation might be the “curvaton”, a field different from the inflaton field. To keep the effective mass of the curvaton small enough compared to the Hubble rate during inflation one may not invoke supersymmetry since the latter is broken by the vacuum energy density. In this paper we propose the idea that the curvaton is a pseudo Nambu-Goldstone boson (PNGB) so that its potential and mass vanish in the limit of unbroken symmetry. We show that the curvaton can be either identified with the extra-component of a gauge field in a compactified five-dimensional theory, a Wilson line, or it may come from a Little-Higgs mechanism. We also analyze the case in which the curvaton is a string axion where supersymmetry is essential.