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arXiv 1807.10620astro-ph.COastro-ph.GAastro-ph.SRgr-qchep-th
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随机引力波背景通过质量结构扩散的极化

Polarization of a stochastic gravitational wave background through diffusion by massive structures

Giulia Cusin, Ruth Durrer, Pedro G. Ferreira

摘要:

传统上用于研究引力波在弯曲背景上传播的几何光学近似在紧凑和扩展的天体附近失效,在那里会发生像扩散和偏振产生这样的波动效应。我们提供了一个框架来研究在非均匀宇宙中传播的引力波的随机背景偏振的产生。该框架是通用的,可以适用于宇宙学和天体物理引力波背景在任何频率范围。我们推导出一个数量级的宇宙学和天体物理背景下产生的偏振量的估计,在目前和计划中的引力波实验所覆盖的频率范围。对于PTA和LISA波段中的天体物理背景,所产生的偏振量被相对于各向异性的因子$10^{-4}$ $(10^{-5})$抑制。对于宇宙学背景,我们得到了额外的$10^{-2}$抑制。我们推测使用我们的方法来映射宇宙中(不可分辨的)结构的分布。

英文摘要:

The geometric optics approximation traditionally used to study the propagation of gravitational waves on a curved background, breaks down in the vicinity of compact and extended astrophysical objects, where wave-like effects like diffusion and generation of polarization occur. We provide a framework to study the generation of polarization of a stochastic background of gravitational waves propagating in an inhomogeneous universe. The framework is general and can be applied to both cosmological and astrophysical gravitational wave backgrounds in any frequency range. We derive an order of magnitude estimate of the amount of polarization generated for cosmological and astrophysical backgrounds, in the frequency range covered by present and planned gravitational wave experiments. For an astrophysical background in the PTA and LISA band, the amount of polarization generated is suppressed by a factor $10^{-4}$ $(10^{-5})$ with respect to anisotropies. For a cosmological background we get an additional $10^{-2}$ suppression. We speculate on using our approach to map the distribution of (unresolvable) structures in the Universe.

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