Generic analysis of kinetically driven inflation

TL;DR

This paper provides a model-independent framework for analyzing kinetically driven inflation, evaluating background evolution, quantum fluctuations, and spectral index, and identifies conditions for viable models with or without shift symmetry.

Contribution

It introduces a generic, model-independent formalism for kinetically driven inflation, including criteria for model viability and the impact of shift symmetry breaking.

Findings

Shift-symmetric KDI models cannot produce observationally consistent quantum fluctuations.

Breaking shift symmetry allows for viable KDI models with conditions for graceful exit.

The formalism encompasses Generalized G-inflation and Ghost inflation.

Abstract

We perform a model-independent analysis of kinetically driven inflation (KDI) which (partially) includes Generalized G-inflation and Ghost inflation. We evaluate the background evolution splitting into the inflationary attractor and the perturbation around it. We also consider the quantum fluctuation of scalar mode with a usual scaling and derive the spectral index ignoring the contribution from the second order products of slow-roll parameters. Using these formalisms, we find that within our generic framework, the models of KDI which possess the shift symmetry of scalar field cannot create the quantum fluctuation consistent to the observation. Breaking the shift symmetry, we obtain a few essential conditions for viable models of KDI associated with the graceful exit.