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arXiv 0812.1537gr-qc
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圈量子引力体积算符的半经典分析:I.通量相干态

Semiclassical analysis of the Loop Quantum Gravity volume operator: I. Flux Coherent States

C. Flori, T. Thiemann

摘要:

体积算符在圈量子引力(LQG)的量子动力学中起着关键的作用,无论是在完整的理论中,还是在适用于宇宙学情况的圈量子宇宙学(LQC)的截断模型中。因此,检查它的半经典极限是否与经典体积算符加上量子修正相一致是至关重要的。在本文中,我们调查这个问题,通过推广和采用先前定义的相干态LQG来自一个圆柱一致定义的复杂化算子,这是一个已知的经典函数的量子化。由于LQG希尔伯特空间的不可分性,这些相干态是不可归一化的,但它们根据有限图定义了唯一定义的截止态。我们的分析结果是,依赖于一个只有n价顶点的图的相干态的体积算符的期望值再现其经典值在相空间点处的相干态的峰值,只有当n = 6。换句话说,由这些状态定义的LQG的半经典扇区由具有立方拓扑的图描述!这与目前的自旋泡沫模型有一定的关系,这些模型都是基于四价边界自旋网络的。

英文摘要:

The volume operator plays a pivotal role for the quantum dynamics of Loop Quantum Gravity (LQG), both in the full theory and in truncated models adapted to cosmological situations coined Loop Quantum Cosmology (LQC). It is therefore crucial to check whether its semiclassical limit coincides with the classical volume operator plus quantum corrections. In the present article we investigate this question by generalizing and employing previously defined coherent states for LQG which derive from a cylindrically consistently defined complexifier operator which is the quantization of a known classical function. These coherent states are not normalizable due to the non separability of the LQG Hilbert space but they define uniquely define cut off states depending on a finite graph. The result of our analysis is that the expectation value of the volume operator with respect to coherent states depending on a graph with only n valent verticies reproduces its classical value at the phase space point at which the coherent state is peaked only if n = 6. In other words, the semiclassical sector of LQG defined by those states is described by graphs with cubic topology! This has some bearing on current spin foam models which are all based on four valent boundary spin networks.

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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