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Enhanced Curvature Perturbation and Primordial Black Hole Formation in Two-stage Inflation with a break

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arxiv 2404.02492 v3 pith:GLTXJSQD submitted 2024-04-03 astro-ph.CO gr-qchep-ph

classification astro-ph.COgr-qchep-ph
keywords findcurvatureinflationperturbationspectrumstagebreakenhanced
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abstract

We investigate a model of $R^2$-gravity with a non-minimally coupled scalar field that gives rise to two-stage inflation with a break, that is, with an intermediate stage where inflation momentarily halts. We find that the power spectrum of the primordial curvature perturbation is significantly enhanced at the break scale, which can account for the primordial black hole (PBH) formation, without affecting the CMB constraint on large scales. The behavior of the curvature perturbation is carefully analyzed and we find a few notable new features in the spectrum. In particular, we find that the $k^3$ growth of the spectrum of toward the end of the first stage of inflation. We argue that this is a universal feature common to all two-stage models where the field dominating the second stage is heavy during the first stage. By appropriately tuning the model parameters, we find that our model can realize the scenario of PBHs as the cold dark matter of the Universe. We also find that we can choose the parameters so that the spectrum of the induced gravitational waves from the enhanced curvature perturbation fits the NANOGrav-15yr data of pulsar timing array observation.

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Cited by 5 Pith papers

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

  1. Superhorizon curvature perturbations in hybrid inflation revisited

    astro-ph.CO 2026-06 unverdicted novelty 6.0 of 10

    Hybrid inflation's waterfall tachyonic instability grows isocurvature modes that convert to curvature perturbations at the field-space turn, yielding a k^{3}-peaked spectrum with always-positive f_NL that enhances PBH...

  2. Reconstructing Primordial Curvature Perturbations via Scalar-Induced Gravitational Waves with LISA

    astro-ph.CO 2025-01 conditional novelty 6.0 of 10

    LISA can reconstruct the primordial curvature power spectrum from scalar-induced gravitational waves, with percent-level precision near the peak and Bayesian tests separating SIGWs from other sources.

  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. A complete analysis of inflation with piecewise quadratic potential

    astro-ph.CO 2024-12 conditional novelty 5.0 of 10

    A new parameter alpha governs the amplitude, slope, and dip of the curvature power spectrum in piecewise quadratic two-stage inflation, with maximum growth k^5(log k)^2.

  5. Gravitational Waves from Primordial Black Holes formed by Null Energy Condition Violation during Inflation

    gr-qc 2026-02 conditional novelty 4.0 of 10

    A transient null-energy-condition violation during inflation is shown to produce a four-component gravitational-wave background — primordial, scalar-induced, PBH ringdown, and binary-merger — with only the solar-mass ...

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