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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

Intermittent null energy condition violations during inflation and primordial gravitational waves

classification gr-qc astro-ph.COhep-th
keywords inflationgravitationalprimordialspectrumbackgroundbandconditionenergy
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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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

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  1. Inverse-k Primordial Oscillations from a Symbolic Regression Search

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  2. DeepInflation: an AI agent for research and model discovery of inflation

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  3. Does Eternal Inflation Violate the Smeared Null Energy Condition?

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    In canonical single-field eternal inflation, stochastic upward fluctuations do not violate the SNEC within the semiclassical slow-roll regime due to parametrically bounded drift and a strong timescale hierarchy N_SNEC ≫ N_BR.

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

    gr-qc 2026-02 conditional novelty 4.0

    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 ...