Multi-field G-inflation

TL;DR

This paper extends G-inflation to multiple fields using covariant multi-galileons, analyzes cosmological perturbations, and clarifies the limitations of the generalized covariant multi-galileon theory.

Contribution

It introduces a multi-field G-inflation framework based on covariant multi-galileons, providing new insights into second-order field equations and perturbation analysis.

Findings

Multi-field DBI galileon inflation is not encompassed by the multi-field generalized G-inflation.

The covariant multi-galileon theory is not the most general second-order multi-scalar-tensor theory.

The quadratic action for cosmological perturbations is explicitly computed.

Abstract

We propose a multi-field extension of (generalized) G-inflation, based on covariant multi-galileons and their generalization preserving second-order field equations. We compute the quadratic action for cosmological perturbations. By comparing the formulas for cosmological perturbations, it is highlighted that multi-field DBI galileon inflation is not included in the multi-field version of generalized G-inflation. Our result indicates that the generalized covariant multi-galileon theory is not the most general multi-scalar-tensor theory with second-order field equations.