# The Curvature Perturbation in the Axion-type Curvaton Model - Astrophysics > Cosmology and Nongalactic Astrophysics

The Curvature Perturbation in the Axion-type Curvaton Model - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We study the axion-type curvaton model, with emphasis on the large fieldregime where analytic results are very difficult to obtain. We evaluate thetensor-scalar ratio $r$ using WMAP normalization and the non-linearityparameters $f {NL}$ and $g {NL}$ by solving the equations numerically using the$\delta N$ formalism. We compare them with results for the curvaton withquadratic potential. We find that $r$ is much smaller for the axion-type casecompared to the result from the quadratic potential, with the differenceincreasingly more pronounced at larger field values. $g {NL}$ is found to bepositive, unlike the quadratic case where it is negative, and the amplitude of$g {NL}$ is much larger. Moreover, there is a nearly linear scaling between$g {NL}$ and $f {NL}$, with small deviation from linearity at large fieldvalues. The slope between $g {NL}$ and $f {NL}$ depends on the parameterscharacterizing the axion-type curvaton model. We further consider a mixedscenario where both the inflaton and the curvaton contribute to the primordialpower spectrum and the non-Gaussianity parameters are found to be much largerthan those in the case with quadratic potential.

Author: Pravabati Chingangbam, Qing-Guo Huang

Source: https://arxiv.org/