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Intermittent null energy condition violations during inflation and primordial gravitational waves

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arxiv 2012.11304 v2 pith:N27N6CCJ submitted 2020-12-21 gr-qc astro-ph.COhep-th

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

Primordial null energy condition (NEC) violation would imprint a blue-tilted spectrum on gravitational wave background (GWB). However, its implications on the GWB might be far richer than expected. We present a scenario, in which after a slow-roll (NEC-preserving) inflation with Hubble parameter $H\simeq H_{inf1}$, the Universe goes through an NEC-violating period and then enters subsequent slow-roll inflation with a higher $H$ ($=H_{inf2}\gg H_{inf1}$). The resulting primordial gravitational wave spectrum is nearly flat at the cosmic microwave background band, as well as at the frequency $f\sim 1/{\rm yr}$ but with higher amplitude (compatible with the recent NANOGrav result). It is also highlighted that for the multi-stage inflation if the NEC violations happened intermittently, we might have a Great Wall-like spectrum of the stochastic GWB at the corresponding frequency band.

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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

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    Combining ACT DR6, SPT-3G D1, and Planck CMB data tightens the 95% upper limits on primordial oscillation amplitudes to about 0.029, with no significant signal.

  4. 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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