arXiv 2104.142312021-04astro-ph.COgr-qchep-phhep-th

随机引力波背景中的干涉

Interferences in the Stochastic Gravitational Wave Background

Disrael Camargo Neves da Cunha, Christophe Ringeval

备注：: 40 pages, 7 figures, uses jcappub. References and discussions added, matches published version
发表信息：: JCAP 2108:005,2021
DOI：: 10.1088/1475-7516/2021/08/005

摘要：

虽然宇宙的膨胀明确地打破了时间平移对称性，但对随机引力波背景（SGWB）的宇宙学预测通常是在所谓的稳态假设下得出的。通过放弃这一假设，并保持在所有长度尺度的引力波的时间依赖性的跟踪，我们推导出预期的不等时（和等时）的SGWB产生的标度源，如宇宙缺陷的波形。对于灭绝和光滑足够的源，我们表明，所有可观察到的量是唯一的，并通过解析确定的各向异性应力相关的全纯傅立叶变换。应变功率谱和能量密度参数都显示出振荡的精细结构，它们在大尺度上显著不同，而在大波数$k$处反相运行。然后，我们讨论的缩放源，从来没有灭绝，也不顺利，并产生一个奇异的傅立叶变换的各向异性应力相关器。对于这些，我们发现在上述精细结构的顶部出现干扰，以及在小尺度下的非典型行为。例如，我们期望在物质时代由长宇宙弦产生的重新标度的应变功率谱$k^2 \mathcal{P}_h$围绕标度不变的平台振荡。这些奇异的来源也被证明产生数量级之间的差异的重新缩放的应变谱和能量密度参数表明，只有前者应该被用于作出可靠的可观察的预测。最后，我们讨论了如何测量这样一个精细结构的SGWB可以消除可能的宇宙学来源。

英文摘要：

Although the expansion of the Universe explicitly breaks the time-translation symmetry, cosmological predictions for the stochastic gravitational wave background (SGWB) are usually derived under the so-called stationary hypothesis. By dropping this assumption and keeping track of the time dependence of gravitational waves at all length scales, we derive the expected unequal-time (and equal-time) waveform of the SGWB generated by scaling sources, such as cosmic defects. For extinct and smooth enough sources, we show that all observable quantities are uniquely and analytically determined by the holomorphic Fourier transform of the anisotropic stress correlator. Both the strain power spectrum and the energy density parameter are shown to have an oscillatory fine structure, they significantly differ on large scales while running in phase opposition at large wavenumbers $k$. We then discuss scaling sources that are never extinct nor smooth and which generate a singular Fourier transform of the anisotropic stress correlator. For these, we find the appearance of interferences on top of the above-mentioned fine-structure as well as atypical behaviour at small scales. For instance, we expect the rescaled strain power spectrum $k^2 \mathcal{P}_h$ generated by long cosmic strings in the matter era to oscillate around a scale invariant plateau. These singular sources are also shown to produce orders of magnitude difference between the rescaled strain spectra and the energy density parameter suggesting that only the former should be used for making reliable observable predictions. Finally, we discuss how measuring such a fine structure in the SGWB could disambiguate the possible cosmological sources.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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