On Non-Canonical Kinetic Terms and the Tilt of the Power Spectrum

Abstract

We argue that in models of inflation with two scalar fields and non-canonical kinetic terms there is a possibility of obtaining a red tilt of the power spectrum of curvature perturbations from noncanonicality-induced interactions between the curvature and isocurvature perturbations. We describe an extremely simple model realizing this idea, study numerically its predictions for the perturbations and discuss applications in realistic scenarios of inflation. We discuss to what extent in this model the scale of the inflationary potential can be decoupled from the amplitude of the density fluctuations.

Figures (1)

• Figure 1: (a) Evolution of the instantaneous curvature and isocurvature perturbations shown in terms of the power spectra. Initial conditions are imposed 8 efolds before the Hubble radius exit at $N=0$. Solid lines $\mathcal{R}$ and $\mathcal{S}$ show the total curvature and isocurvature perturbations. Dashed lines $\mathcal{R_S}$ ($\mathcal{S_R}$) correspond to the components of the curvature (isocurvature) perturbations generated from initial pure isocurvature (curvature) perturbations. (b) Comparison of the curvature ($\mathcal{R}$) and isocurvature ($\mathcal{S}$) modes with different wave numbers, leaving the Hubble radius at $N=0,1,2$.