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arXiv 1402.4350gr-qcastro-ph.CO
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非线性相对论对宇宙学弱透镜收敛的贡献

Non-linear relativistic contributions to the cosmological weak-lensing convergence

Sambatra Andrianomena, Chris Clarkson, Prina Patel, Obinna Umeh, Jean-Philippe Uzan

摘要:

相对论对结构形成动力学的贡献有多种形式,并可能在100 Mpc的典型尺度上对标准图像进行修正。这些修正无法通过牛顿数值模拟获得,因此准确估计这些相对论效应的大小很重要。密度波动耦合产生了一个比任何原始背景都大的引力波背景。类似的相互作用产生了更大的矢量模谱,代表时空的标架拖曳旋转。这些可以在一致性模型中的百分比级别上以低于相等尺度的尺度更改度量。矢量模通过大尺度结构改变背景星系的透镜效应。这在原则上给出了在宇宙学尺度上测量相对论性坐标系拖曳效应的令人兴奋的可能性。计算了非线性张量和矢量模式对宇宙收敛的影响,并将其与来自密度波动、多普勒透镜和较小的萨克斯-沃尔夫效应的一阶透镜贡献进行了比较。由于引力波的透镜效应可以忽略不计,所以我们集中研究矢量模。我们展示了这对于未来的调查,如欧几里得和SKA的相对重要性。我们发现,这些非线性效应对整体弱透镜信号的影响很小,因此在大多数分析中可以安全地忽略它们,尽管它们仍然比线性Sachs-Wolfe项大得多。二阶矢量贡献在中等红移下可以支配一阶多普勒透镜项,并且实际上对于像SKA这样的巡天几何更重要。

英文摘要:

Relativistic contributions to the dynamics of structure formation come in a variety of forms, and can potentially give corrections to the standard picture on typical scales of 100 Mpc. These corrections cannot be obtained by Newtonian numerical simulations, so it is important to accurately estimate the magnitude of these relativistic effects. Density fluctuations couple to produce a background of gravitational waves, which is larger than any primordial background. A similar interaction produces a much larger spectrum of vector modes which represent the frame-dragging rotation of spacetime. These can change the metric at the percent level in the concordance model at scales below the equality scale. Vector modes modify the lensing of background galaxies by large-scale structure. This gives in principle the exciting possibility of measuring relativistic frame dragging effects on cosmological scales. The effects of the non-linear tensor and vector modes on the cosmic convergence are computed and compared to first-order lensing contributions from density fluctuations, Doppler lensing, and smaller Sachs-Wolfe effects. The lensing from gravitational waves is negligible so we concentrate on the vector modes. We show the relative importance of this for future surveys such as Euclid and SKA. We find that these non-linear effects only marginally affect the overall weak lensing signal so they can safely be neglected in most analyses, though are still much larger than the linear Sachs-Wolfe terms. The second-order vector contribution can dominate the first-order Doppler lensing term at moderate redshifts and are actually more important for survey geometries like the SKA.

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