UV artefacts in ultra-slow-roll models of inflation
Abstract
Within single-field inflation, primordial black hole and scalar-induced gravitational wave production from enhanced primordial perturbations typically requires a transient non-attractor phase, such as ultra-slow roll. We investigate the physical consistency of modeling such scenarios through analytical Hubble-flow parametrisation. By reconstructing the underlying scalar field potential, we show that even slow transitions in the slow-roll parameters can hide sharp, localised spikes in higher-order derivatives of the potential at the transition from ultra-slow-roll to slow-roll. These are typically not found in analytic potentials. To evaluate the impact of these structures, we implement a UV-filtering procedure based on discrete Fourier transform to systematically suppress high frequency modes in field space in both classes of models. We find that the filter effectively removes sharp features in Hubble-flow-derived potentials. As a consequence, we show that UV-filtered models typically respect Wands duality invariance as the field evolves back from ultra-slow roll to slow roll. Beyond linear perturbation theory, the introduction of spurious UV effects might affect other observables, such as non-Gaussianity and loop contributions. Our results thereby question the robustness of simple analytical Hubble-flow parametrisation for modeling inflationary models with a transient non-attractor phase.
Related
- Ultra-slow-roll Inflation with Non-perturbative Non-Gaussianity and Scalar Induced Gravitational Waves
- Running into tension: primordial black holes from ultra-slow-roll inflation, spectral running, and the Hubble tension
- Analytic results for slow-roll curved-space inflation and exponential potentials
- Constant-Roll Inflation as a Competitive Alternative to Slow-Roll Inflation
- A Global Overview of Starobinsky Inflation beyond slow-roll with CMB-BAO data
BibTeX
@misc{barnert2026artefacts,
title = {{UV artefacts in ultra-slow-roll models of inflation}},
author = {Gerald Barnert and Laura Iacconi and Hooshyar Assadullahi and Kazuya Koyama and David Wands},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.28005},
eprint = {2606.28005},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.28005},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - UV artefacts in ultra-slow-roll models of inflation
AU - Gerald Barnert
AU - Laura Iacconi
AU - Hooshyar Assadullahi
AU - Kazuya Koyama
AU - David Wands
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2606.28005
UR - https://arxiv.org/abs/2606.28005
AB - Within single-field inflation, primordial black hole and scalar-induced gravitational wave production from enhanced primordial perturbations typically requires a transient non-attractor phase, such as ultra-slow roll. We investigate the physical consistency of modeling such scenarios through analytical Hubble-flow parametrisation. By reconstructing the underlying scalar field potential, we show that even slow transitions in the slow-roll parameters can hide sharp, localised spikes in higher-order derivatives of the potential at the transition from ultra-slow-roll to slow-roll. These are typically not found in analytic potentials. To evaluate the impact of these structures, we implement a UV-filtering procedure based on discrete Fourier transform to systematically suppress high frequency modes in field space in both classes of models. We find that the filter effectively removes sharp features in Hubble-flow-derived potentials. As a consequence, we show that UV-filtered models typically respect Wands duality invariance as the field evolves back from ultra-slow roll to slow roll. Beyond linear perturbation theory, the introduction of spurious UV effects might affect other observables, such as non-Gaussianity and loop contributions. Our results thereby question the robustness of simple analytical Hubble-flow parametrisation for modeling inflationary models with a transient non-attractor phase.
ER -