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arXiv 2011.08859gr-qchep-th
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从时空的量子微结构看介观尺度下的引力有效action

Gravitational effective action at mesoscopic scales from the quantum microstructure of spacetime

T. Padmanabhan

摘要:

在介观尺度下,量子校正的引力场方程应该是通过对与给定几何结构一致的前几何变量的微观组态的数目进行极值化($Ω$)而产生的。该$Ω$又是与每个事件P相关联的微观构型的密度$ρ(P)$在所有事件P上的乘积。人们会期望$ρ\propto\sqrt{g}$,使得$ρd^4x$缩放为区域的适当体积。另一方面,在首阶,我们期望极值原理是基于希尔伯特作用量的,这意味着$\lnρ\propto R$。我展示了如何这两个明显矛盾的要求可以通过使用曲率的函数依赖性$\sqrt{g}$,在黎曼法坐标(RNC),和粗粒化普朗克尺度。这导致微观构型的密度为$ρ= Δ^{-1} = \sqrt{g}_{RNC}$,其中$Δ$是粗粒Van-Vleck行列式。该办法还规定:(a)计算场方程的QG修正的系统方法;(b)引力的有效作用量与时空流体的动力学理论之间的直接联系。

英文摘要:

At mesoscopic scales, the quantum corrected field equations of gravity should arise from extremizing, $Ω$, the number of microscopic configurations of pre-geometric variables consistent with a given geometry. This $Ω$, in turn, is the product over all events P of the density, $ρ(P)$, of microscopic configurations associated with each event P. One would have expected $ρ\propto\sqrt{g}$ so that $ρd^4x$ scales as the proper volume of a region. On the other hand, at leading order, we would expect the extremum principle to be based on the Hilbert action, suggesting $\lnρ\propto R$. I show how these two apparently contradictory requirements can be reconciled by using the functional dependence of $\sqrt{g}$ on curvature, in the Riemann normal coordinates (RNC), and coarse-graining over Planck scales. This leads to the density of microscopic configurations to be $ρ= Δ^{-1} = \sqrt{g}_{RNC}$ where $Δ$ is the coarse grained Van-Vleck determinant. The approach also provides: (a) systematic way of computing QG corrections to field equations and (b) a direct link between the effective action for gravity and the kinetic theory of the spacetime fluid.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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