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arXiv · 2605.27505

On the Validity of the Effective Theory of (Multi-)Field Inflation

Andrea Ambrosi de Magistris·Alberto Salvio
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Abstract

Motivated by trans-Planckian issues in inflation, we determine the Hilbert space and amplitudes of quantum perturbations in the general low-energy effective theory of (multi-)field inflation without relying on the sub-horizon limit. The scalar sector is the most intricate, featuring field mixings and second-class constraints, which we handle using Dirac brackets. These results enable us to estimate the magnitude of higher-derivative corrections. In the specific case of slow-roll inflation, such estimate can be expressed in terms of the first slow-roll parameter $\epsilon$ for a given cutoff $\Lambda$. We apply our results to several inflationary models with finite $\Lambda$: Higgs inflation, the Starobinsky model, natural inflation and hilltop inflation.

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Andrea Ambrosi de Magistris, Alberto Salvio. 2026-05-26. On the Validity of the Effective Theory of (Multi-)Field Inflation. https://arxiv.org/abs/2605.27505

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