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arXiv 1312.4458astro-ph.COgr-qc
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由光度距离确定大尺度结构的新方法

A new method to determine large scale structure from the luminosity distance

Antonio Enea Romano, Hsu-Wen Chiang, Pisin Chen

摘要:

光度距离可以用来确定观测者周围大尺度结构的性质。为此,我们开发了一种新的反演方法来映射亮度距离的LTB度量的基础上使用的爱因斯坦方程的精确解析解。这种方法的主要优点是一个改进的数值精度和稳定性,一个精确的分析设置的初始条件的微分方程,需要解决和有效性的任何符号的功能确定的LTB几何。由于微分方程具有完全解析的形式,该方法还简化了在数值解变得不稳定的视视界点附近红移展开的计算。我们通过反演超新星Ia光度距离函数来测试该方法,该函数对应于最佳拟合的$ΛCDM$模型。我们发现,只有一个有限的范围内的初始条件是兼容的观察,或从红色到蓝移的过渡可以发生在相对较低的红移。尽管没有宇宙学常数的LTB解已被证明与所有不同的可用观测数据集不相容,但这些研究通常拟合数据,假设不均匀性轮廓的特殊函数拟合,这通常仅取决于几个参数。相反,反演方法能够充分探索确定LTB解的函数的自由度。另一个重要的可能的应用不是关于LTB解决方案作为宇宙学模型,而是作为工具来研究位于宇宙非均匀区域的一般观测者所做的观测的影响,其中需要完全非微扰处理,包括爱因斯坦方程的精确解。

英文摘要:

The luminosity distance can be used to determine the properties of large scale structure around the observer. To this purpose we develop a new inversion method to map luminosity distance to a LTB metric based on the use of the exact analytical solution for Einstein equations. The main advantages of this approach are an improved numerical accuracy and stability, an exact analytical setting of the initial conditions for the differential equations which need to be solved and the validity for any sign of the functions determining the LTB geometry. Given the fully analytical form of the differential equations, this method also simplifies the calculation of the red-shift expansion around the apparent horizon point where the numerical solution becomes unstable. We test the method by inverting the supernovae Ia luminosity distance function corresponding to the the best fit $ΛCDM$ model. We find that only a limited range of initial conditions is compatible with observations, or a transition from red to blue shift can occur at relatively low redshift. Despite LTB solutions without a cosmological constant have been shown not to be compatible with all different set of available observational data, those studies normally fit data assuming a special functional ansatz for the inhomogeneity profile, which often depend only on few parameters. Inversion methods on the contrary are able to fully explore the freedom in fixing the functions which determine a LTB solution. Another important possible application is not about LTB solutions as cosmological models, but rather as tools to study the effects on the observations made by a generic observer located in an inhomogeneous region of the Universe where a fully non perturbative treatment involving exact solutions of Einstein equations is required.

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