Resurrecting power law inflation in the light of Planck results

TL;DR

This paper introduces a novel non-canonical scalar field model for power law inflation that aligns with Planck data on tensor-to-scalar ratio, spectral index, and non-Gaussianity, and also addresses the graceful exit problem.

Contribution

It proposes a new power law inflation model with a non-canonical scalar field that matches observational constraints and solves the exit problem.

Findings

Model matches Planck constraints on tensor-to-scalar ratio and spectral index.

The non-canonical kinetic term allows for successful inflation and exit.

Extension of the model resolves the graceful exit problem.

Abstract

It is well known that a canonical scalar field with an exponential potential can drive power law inflation (PLI). However, the tensor-to-scalar ratio in such models turns out to be larger than the stringent limit set by recent Planck results. We propose a new model of power law inflation for which the scalar spectra index, the tensor-to-scalar ratio and the non-gaussianity parameter $f_{_{\mathbf{NL}}}^{\mathrm{equil}}$ are in excellent agreement with Planck results. Inflation, in this model, is driven by a non-canonical scalar field with an inverse power law potential. The Lagrangian for our model is structurally similar to that of a canonical scalar field and has a power law form for the kinetic term. A simple extension of our model resolves the graceful exit problem which usually afflicts models of power law inflation.