Primordial non-Gaussianity from G-inflation

Abstract

We present a comprehensive study of primordial fluctuations generated from G-inflation, in which the inflaton Lagrangian is of the form $K(\varphi ,X)-G(\varphi ,X)\square \varphi$ with $X=-(\partial \varphi {)}^2/2$. The Lagrangian still gives rise to second-order gravitational and scalar field equations, and thus offers a more generic class of single-field inflation than ever studied, with a richer phenomenology. We compute the power spectrum and the bispectrum, and clarify how the non-Gaussian amplitude depends upon parameters such as the sound speed. In so doing we try to keep as great generality as possible, allowing for non slow-roll and deviation from the exact scale-invariance.

12 pages; v2: Minor changes, added 4 figures, matches the published version

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• Symmetries for Galileons and DBI scalars on curved space