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Induced gravitational waves as a probe of thermal history of the universe

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arxiv 2005.12314 v2 pith:YJNT74TV submitted 2020-05-25 gr-qc astro-ph.COhep-th

classification gr-qcastro-ph.COhep-th
keywords spectrumgravitationaluniverseinducedbrokenequationpeakpower-law
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

The scalar perturbation induced gravitational waves are a probe of the primordial density perturbation spectrum on small scales. In this paper, we show that they can also probe the thermal history of the universe. We assume the universe underwent a stage with a constant equation of state parameter $w$, followed by the radiation-dominated stage of the conventional big bang universe. We find that the infrared slope of the power spectrum of the induced stochastic gravitational wave background for decelerating cosmologies is related to the equation of state of the universe. Furthermore, the induced gravitational wave spectrum has in general a broken power-law shape around the scale of reheating. Interestingly, below the threshold $w=0$ of the equation of state parameter, the broken power-law presents a peak for a Dirac delta peak in the scalar spectrum. For a finite width peak, the threshold changes to $w=-1/15$ depending on the value of the width. In some cases, such a broken power-law gravitational wave spectrum may degenerate to the spectrum from other sources like phase transitions or global cosmic strings.

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Cited by 6 Pith papers

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

  1. Observable Gravitational Wave Strain at Second Order

    gr-qc 2025-12 conditional novelty 7.0 of 10

    At second order, the gravitational-wave strain measured by geodesic observers exchanging light pulses is the transverse-traceless metric perturbation in the Newton gauge (h_N^(2)).

  2. Primordial Black Hole from Tensor-induced Density Fluctuation: First-order Phase Transitions and Domain Walls

    astro-ph.CO 2026-05 unverdicted novelty 6.0 of 10

    Tensor perturbations from FOPT and domain-wall sources are claimed to induce second-order scalar perturbations large enough to form primordial black holes, potentially all of the dark matter.

  3. Alternative LISA-TAIJI networks: Detectability of the Parity Violation in Stochastic Gravitational Wave Background

    gr-qc 2024-12 accept novelty 6.0 of 10

    The LISA-TAIJIm configuration, with TAIJI's constellation inclined opposite to LISA's, is about an order of magnitude more sensitive to a circularly polarized stochastic gravitational wave background at low frequencie...

  4. Scalar-induced gravitational waves from a box-shaped curvature power spectrum

    gr-qc 2026-07 accept novelty 5.5 of 10

    Analytic SIGW spectra for a log-box curvature power spectrum: narrow-box geometric overlap factor turning IR slope k^{3}ln^{2}k into k^{2}ln^{2}k, plus broad-box product of universal edge functions.

  5. Non-Standard Thermal History and Formation of Primordial Black Holes in Einstein-Gauss-Bonnet Gravity

    gr-qc 2025-01 conditional novelty 5.0 of 10

    A tuned Einstein-Gauss-Bonnet inflation model can create primordial black holes from asteroid-sized to tens of solar masses and secondary gravitational waves, with abundances that change dramatically in a stiff post-i...

  6. Tensor induced gravitational waves

    astro-ph.CO 2025-07 conditional novelty 4.0 of 10

    Second-order tensor-induced gravitational waves can shift the inferred parameters of small-scale primordial gravitational wave models fitted to NANOGrav 15-year data, with one model favored by Bayes factors.

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