在大尺度结构勘测中观测相对论特征-- II：相对论模拟系综中的多普勒放大
Observing relativistic features in large-scale structure surveys -- II: Doppler magnification in an ensemble of relativistic simulations
摘要：
标准的宇宙学模型本质上是相对论性的，但从本质上讲，牛顿理论可以准确地预测大范围的宇宙学观测。然而，在宇宙视界大小的“超大”距离尺度上，情况并非如此，在这种尺度上，相对论效应再也不能被忽略。在本文中，我们提出了一套新的53完全相对论模拟生成的gevolution代码，每个覆盖了整个天空到$z \approx$ 0.85，大约1930平方度到$z \approx$ 3.55。其中包括对大质量中微子的相对论处理，以及可以用来精确计算过去光锥上的可观测量的引力势。模拟分为两组，第一组是39个模拟相同的基准宇宙学（基于Euclid Flagship 2宇宙学），具有不同的初始条件实现，第二组固定初始条件，但依次改变七个宇宙学参数。总之，这些模拟使我们能够进行统计研究，并计算相对于宇宙学参数的任何相对论观测的衍生物。作为一个例子的应用，我们计算的多普勒放大项之间的互相关收敛，$κ_v$，和CDM+重子密度对比，$δ_{\rm cb}$，这只出现在一个（特殊）相对论处理。我们能够准确地恢复这一项的预测相对论微扰理论，并研究其样本方差和衍生物相对于宇宙学参数。
英文摘要：
The standard cosmological model is inherently relativistic, and yet a wide range of cosmological observations can be predicted accurately from essentially Newtonian theory. This is not the case on `ultra-large' distance scales, around the cosmic horizon size, however, where relativistic effects can no longer be neglected. In this paper, we present a novel suite of 53 fully relativistic simulations generated using the gevolution code, each covering the full sky out to $z \approx$ 0.85, and approximately 1930 square degrees out to $z \approx$ 3.55. These include a relativistic treatment of massive neutrinos, as well as the gravitational potential that can be used to exactly calculate observables on the past light cone. The simulations are divided into two sets, the first being a set of 39 simulations of the same fiducial cosmology (based on the Euclid Flagship 2 cosmology) with different realisations of the initial conditions, and the second which fixes the initial conditions, but varies each of seven cosmological parameters in turn. Taken together, these simulations allow us to perform statistical studies and calculate derivatives of any relativistic observable with respect to cosmological parameters. As an example application, we compute the cross-correlation between the Doppler magnification term in the convergence, $κ_v$, and the CDM+baryon density contrast, $δ_{\rm cb}$, which arises only in a (special) relativistic treatment. We are able to accurately recover this term as predicted by relativistic perturbation theory, and study its sample variance and derivatives with respect to cosmological parameters.
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