Geometrical Destabilization of Inflation

TL;DR

This paper introduces a universal mechanism where the curvature of the field space manifold can destabilize inflationary trajectories, potentially ending inflation prematurely and impacting cosmological model constraints.

Contribution

It reveals a general geometric destabilization mechanism during inflation caused by field space curvature, affecting model viability and interpretation of observational data.

Findings

Heavy scalar fields can be destabilized by field space curvature.

Higher-order operators can trigger inflationary instability.

Geometrical destabilization imposes constraints on inflationary models.

Abstract

We show the existence of a general mechanism by which heavy scalar fields can be destabilized during inflation, relying on the fact that the curvature of the field space manifold can dominate the stabilizing force from the potential and destabilize inflationary trajectories. We describe a simple and rather universal setup in which higher-order operators suppressed by a large energy scale trigger this instability. This phenomenon can prematurely end inflation, thereby leading to important observational consequences and sometimes excluding models that would otherwise perfectly fit the data. More generally, it modifies the interpretation of cosmological constraints in terms of fundamental physics. We also explain how the geometrical destabilization can lead to powerful selection criteria on the field space curvature of inflationary models.