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arXiv 0809.3314gr-qc
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球对称时空中的准局部变量、非线性扰动和反作用

Quasi-local variables, non-linear perturbations and back-reaction in spherically symmetric spacetimes

Roberto A Sussman

摘要:

我们引入一个准局部积分泛函和标量准局部变量来研究一类球对称非齐次时空,推广了Lemaitre-Tolman-Bondi(LTB)尘埃解(“LTB”时空)。通过使用这些变量,我们可以将流体流动演化方程转化为Friedman-Lemaitre-Robertson-Walker(FLRW)宇宙学的非线性、协变、规范不变扰动的演化方程。在线性极限下,我们得到了长波近似下同步规范中的球微扰。形式主义有一个显着的潜力,宇宙学的应用,因为它允许一个检查各种各样的来源与不同的“状态方程”,推广已知的FLRW解决方案,理想化,但非平凡和非线性非均匀条件。准局部泛函可以被重新表述为加权的真体积平均分布,其权重因子由与准局部质能函数相关的标量不变量给出。在Buchert的适当平均形式主义中出现的反反应项可以表示为平均和准局部能量密度波动之间的差异。通过比较这个平均值与加权准本地的,我们可以定义一个结合能泛函的空间梯度的平均和准本地变量中出现的反反应条款。

英文摘要:

We introduce a quasi-local integral functional and scalar quasi-local variables to examine a wide class of spherically symmetric inhomogeneous spacetimes that generalize the Lemaitre-Tolman-Bondi (LTB) dust solutions ("LTB" spacetimes). By using these variables, we can transform the fluid flow evolution equations into evolution equations for non-linear, covariant, gauge--invariant perturbations of Friedman-Lemaitre-Robertson-Walker (FLRW) cosmologies. In the linear limit, we obtain spherical perturbations in the synchronous gauge under the long wavelength approximation. The formalism has a significant potential for cosmological applications, as it allows one to examine a wide variety of sources with different "equations of state", generalizing known FLRW solutions to idealized but non-trivial and non-linear inhomogeneous conditions. The quasi-local functional can be reformulated as a weighed proper volume average distribution, with the weight factor given by a scalar invariant related to the quasi-local mass-energy function. The back-reaction terms, emerging in Buchert's proper averaging formalism, can be expressed as differences between fluctuations of averaged and quasi-local energy densities. By comparing this average with the weighed quasi-local one, we can define a binding energy functional related to spatial gradients of the averaged and quasi-local variables that appear in the back-reaction terms.

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