Some recent work on the curvaton paradigm

I review the simplest curvaton scenario. Using a pseudo Nambu-Goldstone boson as curvaton avoids the η-problem of inflation which plagues most curvaton candidates. Then I report on a collaboration with E. J. Chun and K. Dimopoulos, describing a concrete realization of the curvaton mechanism. It uses a pseudo Nambu-Goldstone boson can be found in the supersymmetric Peccei-Quinn mechanism resolving the strong CP problem. In the flaton models of Peccei-Quinn symmetry breaking, the angular degree of freedom associated with the QCD axion can naturally be a flat direction during inflation and provides successful curvature perturbations. In this scheme, the preferred values of the axion scale and the Hubble parameter during inflation turn out to be about 1010 GeV and 1012 GeV, respectively. Moreover, it is found that a significant isocurvature component, (anti)correlated to the overall curvature perturbation, can be generated, which is a smoking-gun for the curvaton scenario. Finally, non-Gaussianity in the perturbation spectrum at potentially observable level is also possible.