Beyond $f(\phi)\mathcal{G}$: Gauss--Bonnet inflation with $\mu(\phi,X)$

TL;DR

This paper introduces a trajectory-selective coupling in Gauss--Bonnet inflation that localizes higher-curvature effects to a finite phase space region, enabling controlled and predictable impacts on CMB observables.

Contribution

It proposes a novel gating mechanism (,) to localize Gauss--Bonnet effects during inflation, ensuring stability and observational consistency.

Findings

Stable inflationary solutions with localized Gauss--Bonnet effects identified

The framework allows for controlled higher-curvature effects on CMB scales

Dependence of observables on Gauss--Bonnet strength and gating analyzed

Abstract

Gauss--Bonnet inflation typically affects the dynamics over an extended portion of the trajectory, making it difficult to isolate a controlled imprint at CMB scales. We consider a trajectory-selective coupling \(\mu(\phi,X)\) that gates the Gauss--Bonnet sector in phase space, enabling the higher-curvature contribution to be localized within a finite e-fold window while remaining negligible elsewhere. We identify stable inflationary solutions consistent with this localization and enforce standard ghost and gradient stability conditions for both scalar and tensor perturbations. For these viable backgrounds we compute pivot-scale observables and examine their dependence on the overall Gauss--Bonnet strength and on the kinetic gating. The framework offers a controlled route for realizing localized higher-curvature effects with predictable consequences for CMB-scale measurements.