N-vaton

TL;DR

The paper introduces the N-vaton model, where multiple curvatons from string theory contribute to primordial perturbations, and analyzes its implications for non-Gaussianity and power spectrum features.

Contribution

It proposes the N-vaton scenario with multiple curvatons, calculates primordial spectra using $\, ext{delta}\, ext{N}$ formalism, and explores phenomenological implications in string theory contexts.

Findings

Red tilted power spectrum can be achieved.

Large non-Gaussianity parameter $f_{NL}$ is possible.

String theory axions can serve as curvatons in this model.

Abstract

In general there are a large number of light scalar fields in the theories going beyond standard model, such as string theory, and some of them can be taken as the candidates of curvatons. For simplicity, we assume all of 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 "N-vaton". We use $\delta {\cal N}$ formalism to calculate the primordial power spectrum and bispectrum in 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 $f_{NL}$ can be naturally obtained if the curvature perturbation generated by inflaton also makes a significant contribution to the primordial power spectrum. As a realistic N-vaton model, we suppose that the axions in the KKLT compactifications of Type IIB string theory are taken as curvatons and a rich phenomenology is obtained.