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arXiv 2103.00281astro-ph.COgr-qc
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引力波直接探测不约束CMB尺度的张量谱指数

Gravitational Wave Direct Detection does not Constrain the Tensor Spectral Index at CMB Scales

William H. Kinney

摘要:

我讨论的约束的功率谱的原始张量扰动的组合宇宙微波背景(CMB)的测量和引力波直接探测实验LIGO/处女座和DECIGO。主要有两点:(1)暴胀预言了原始张量谱的近似幂律形式,但没有预言其振幅。由于普朗克和LIGO/Virgo都没有实际探测到原始张量模,因此在当前数据下,张量功率谱的斜率不可能存在与模型无关的约束。(2)CMB和LIGO/Virgo尺度相差超过19个数量级,DECIGO相差16个数量级。我表明,从CMB的直接检测频率的幂律外推高估了原始张量模式的振幅多达两个数量级相对于现实的单场膨胀模型的合奏。此外,直接检测尺度下的原始张量振幅大多与CMB尺度下的张量谱指数无关,并且任何约束都强烈依赖于暴胀势的具体形式。

英文摘要:

I discuss constraints on the power spectrum of primordial tensor perturbations from a combination of Cosmic Microwave Background (CMB) measurements and the gravitational wave direct detection experiments LIGO/Virgo and DECIGO. There are two main points: (1) Inflation predicts an approximately power-law form for the primordial tensor spectrum, but makes no prediction for its amplitude. Given that neither Planck nor LIGO/Virgo has actually detected primordial tensor modes, it is trivially true that no model-independent constraint on the slope of the tensor power spectrum is possible with current data. (2) CMB and LIGO/Virgo scales differ by more than 19 orders of magnitude, and 16 for DECIGO. I show that a power-law extrapolation from CMB to direct detection frequencies overestimates the amplitude of primordial tensor modes by as much as two orders of magnitude relative to an ensemble of realistic single-field inflation models. Moreover, the primordial tensor amplitude at direct detection scales is mostly uncorrelated with the tensor spectral index at CMB scales, and any constraint is strongly dependent on the specific form of the inflationary potential.

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