Speaker
Description
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 modelling such scenarios through analytical Hubble-flow parametrisation. By reconstructing the underlying scalar field potential, we show that even smooth transitions in the slow-roll parameters can hide sharp, localized features in higher-order derivatives 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 to both classes of models. We find that the filter effectively removes sharp features in Hubble-flow-derived potentials, while prototypical analytical potentials remain largely unaffected. As a consequence, we show that UV-filtered models typically preserve Wands duality invariance. 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 soundness of Hubble-flow parametrisation for modelling inflationary models with a transient non-attractor phase.
| Other topic / keywords: | Primordial black holes, Ultra-slow-roll |
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