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How deep is the dip and how tall are the wiggles in inflationary power spectra?

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arxiv 2501.14681 v3 pith:2VZTRHT2 submitted 2025-01-24 astro-ph.CO gr-qchep-ph

classification astro-ph.COgr-qchep-ph
keywords peakpowermodelsscalesspectrumamplitudedampingperturbations
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We study linear scalar perturbations in single-field models of inflation featuring a non-attractor phase. These models lead to a peak in the curvature power spectrum that may result in the formation of primordial black holes. We develop a transfer-matrix formalism, analogous to the S-matrix program in quantum-field theory, that maps perturbations throughout the transitory phase. At scales smaller than the peak, the power spectrum features damped oscillations, and the duration of the transition sets the scale at which power-law damping switches to exponential damping. At scales larger than the peak, we demonstrate that a dip appears in the power spectrum if and only if the inflaton's velocity does not flip sign. We show that the amplitude at the dip always scales as the inverse square-rooted amplitude of the peak, and comment on the physical consequences of this universal relationship. We also test the robustness of our results with a few toy models and interpret them with an intuitive mechanical analogy.

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Cited by 4 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. When inflationary perturbations refuse to classicalise: the role of non-Gaussianity in Wigner negativity

    gr-qc 2026-01 conditional novelty 6.0 of 10

    In ultra-slow-roll inflation, the Wigner function of the inflationary Goldstone field becomes negative and its negativity grows with the scale factor squared, so the perturbations do not automatically become classical.

  2. Axion USR Inflation

    astro-ph.CO 2025-07 conditional novelty 6.0 of 10

    In axion inflation with an intermediate ultra-slow-roll phase, the instability parameter collapses at the start of USR, terminating gauge production and yielding a two-peak power spectrum with P_R ∝ k^m, m>4.

  3. Evolution of Linear Perturbations under Time-Dependent Hubble Friction I: SR-USR-SR Inflation

    gr-qc 2026-02 conditional novelty 5.0 of 10

    Analytic asymptotics show the dip in the SR-USR-SR curvature power spectrum comes from cancellation between two growing modes, not a constant-versus-growing cancellation.

  4. $\delta n$ formalism: A new formulation for the probability density of the curvature perturbation

    astro-ph.CO 2025-05 conditional novelty 5.0 of 10

    A reformulation of the δN formalism that counts e-folds forward and exploits the superhorizon correlation between field and velocity to express the curvature perturbation PDF as a one-dimensional change of variables.

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