Spectral Index in Curvaton Scenario

TL;DR

This paper discusses the challenges of naturally producing a red tilted and large non-Gaussian primordial power spectrum within the curvaton model, highlighting limitations related to initial conditions of inflation.

Contribution

It identifies the inherent difficulty in generating both a red tilt and large non-Gaussianity in the curvaton scenario due to initial condition constraints.

Findings

Red tilted spectrum and large non-Gaussianity are hard to achieve simultaneously in the curvaton model.

The non-Gaussianity parameter $f_{NL}$ is linked to initial inflation conditions.

The model's limitations are highlighted in relation to observational data constraints.

Abstract

A red tilted primordial power spectrum is preferred by WMAP five-year data and a large positive local-type non-Gaussianity $f_{NL}$ might be observed as well. In this short note we find that a red tilted and large non-Gaussian primordial power spectrum cannot be naturally obtained in curvaton model, because $f_{NL}$ is related to the initial condition of inflation.