The N-vaton

In general there are a large number of light scalar fields in the theories going beyond the standard model, such as string theory, and some of them can be considered as curvaton candidates. For simplicity, we assume that all curvatons have the same decay rate and suddenly decay into radiation at the same time. In order to distinguish this scenario from the more general case, we call it the 'N-vaton' scenario. We use delta N formalism to calculate the primordial power spectrum and bispectrum in the N-vaton model and investigate various bounds on the non-Gaussianity parameter f(NL). A red-tilted primordial power spectrum and a large value of fNL can be obtained naturally if the curvature perturbation generated by inflaton also makes a significant contribution to the primordial power spectrum. For a realistic N-vaton model, we suppose that the axions in the Kachru-Kallosh-Linde-Trivedi compactifications of type IIB string theory are taken as the curvatons and a rich phenomenology is obtained.