Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approach

Abstract We revisit one-loop corrections to the power spectrum of curvature perturbations ζ in an inflationary scenario containing a transient ultra-slow-roll (USR) period. In ref. [1], it was argued that one-loop corrections to the power spectrum of ζ can be larger than the tree-level one within th...

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Main Authors: Ryodai Kawaguchi, Shinji Tsujikawa, Yusuke Yamada
Format: Article
Language:English
Published: SpringerOpen 2024-12-01
Series:Journal of High Energy Physics
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Online Access:https://doi.org/10.1007/JHEP12(2024)095
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author Ryodai Kawaguchi
Shinji Tsujikawa
Yusuke Yamada
author_facet Ryodai Kawaguchi
Shinji Tsujikawa
Yusuke Yamada
author_sort Ryodai Kawaguchi
collection DOAJ
description Abstract We revisit one-loop corrections to the power spectrum of curvature perturbations ζ in an inflationary scenario containing a transient ultra-slow-roll (USR) period. In ref. [1], it was argued that one-loop corrections to the power spectrum of ζ can be larger than the tree-level one within the parameter region generating the seeds of primordial black holes during the USR epoch, which implies the breakdown of perturbation theory. We prove that this is not the case by using a master formula for one-loop corrections to the power spectrum obtained in ref. [2]. We derive the same formula within the path-integral formalism, which is simpler than the original derivation in [2]. To show the smallness of one-loop corrections, the consistency relations and the effective constancy of tree-level mode functions of ζ for super-Hubble modes play essential roles, with which the master formula gives a simple expression for one-loop corrections. For concreteness, we provide a reduced set of interactions including the leading-order one, while establishing the consistency relations in a self-consistent manner. We also show how the consistency relations of various operators hold explicitly, which plays a key role in proving the absence of large one-loop corrections.
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spelling doaj-art-e3c2856b2fb44710b51a01ea8e42763d2025-08-20T01:57:11ZengSpringerOpenJournal of High Energy Physics1029-84792024-12-0120241216610.1007/JHEP12(2024)095Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approachRyodai Kawaguchi0Shinji Tsujikawa1Yusuke Yamada2Department of Physics, Waseda UniversityDepartment of Physics, Waseda UniversityWaseda Institute for Advanced Study, Waseda UniversityAbstract We revisit one-loop corrections to the power spectrum of curvature perturbations ζ in an inflationary scenario containing a transient ultra-slow-roll (USR) period. In ref. [1], it was argued that one-loop corrections to the power spectrum of ζ can be larger than the tree-level one within the parameter region generating the seeds of primordial black holes during the USR epoch, which implies the breakdown of perturbation theory. We prove that this is not the case by using a master formula for one-loop corrections to the power spectrum obtained in ref. [2]. We derive the same formula within the path-integral formalism, which is simpler than the original derivation in [2]. To show the smallness of one-loop corrections, the consistency relations and the effective constancy of tree-level mode functions of ζ for super-Hubble modes play essential roles, with which the master formula gives a simple expression for one-loop corrections. For concreteness, we provide a reduced set of interactions including the leading-order one, while establishing the consistency relations in a self-consistent manner. We also show how the consistency relations of various operators hold explicitly, which plays a key role in proving the absence of large one-loop corrections.https://doi.org/10.1007/JHEP12(2024)095Cosmological modelsde Sitter space
spellingShingle Ryodai Kawaguchi
Shinji Tsujikawa
Yusuke Yamada
Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approach
Journal of High Energy Physics
Cosmological models
de Sitter space
title Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approach
title_full Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approach
title_fullStr Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approach
title_full_unstemmed Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approach
title_short Proving the absence of large one-loop corrections to the power spectrum of curvature perturbations in transient ultra-slow-roll inflation within the path-integral approach
title_sort proving the absence of large one loop corrections to the power spectrum of curvature perturbations in transient ultra slow roll inflation within the path integral approach
topic Cosmological models
de Sitter space
url https://doi.org/10.1007/JHEP12(2024)095
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AT shinjitsujikawa provingtheabsenceoflargeoneloopcorrectionstothepowerspectrumofcurvatureperturbationsintransientultraslowrollinflationwithinthepathintegralapproach
AT yusukeyamada provingtheabsenceoflargeoneloopcorrectionstothepowerspectrumofcurvatureperturbationsintransientultraslowrollinflationwithinthepathintegralapproach