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arXiv 1209.4892gr-qchep-th
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Barbero-Immirzi参数在离散量子引力中的作用

On the role of the Barbero-Immirzi parameter in discrete quantum gravity

Bianca Dittrich, James P. Ryan

摘要:

Barbero和Immirzi提出的单参数变换族在量子引力的非微扰方法中起着重要作用,其中包括圈量子引力和自旋泡沫。它有利于循环量化方案,随后的Barbero-Immirzi参数(伽马)出现在两个光谱的几何算子和自旋泡沫提供的动力学。然而,关于量子物理是否应该依赖于Barbero-Immirzi参数的争论仍在继续。从离散的SO(4)-BF理论相空间出发,我们找到了两种可能的简化。第一个减少到一个相空间与伽玛相关的辛结构,更一般地与相空间的基础环量子引力限制到一个单一的图形- a.k.a.扭曲的几何体。第二,更充分的减少导致一个伽玛独立的辛结构的相空间的分段平坦的线性几何- a.k.a. Regge几何。因此,物理预测的伽马依赖性与量子化下相空间的选择有关。

英文摘要:

The 1-parameter family of transformations identified by Barbero and Immirzi plays a significant role in non-perturbative approaches to quantum gravity, among them Loop Quantum Gravity and Spin Foams. It facilitates the loop quantization programme and subsequently the Barbero-Immirzi parameter (gamma) arises in both the spectra of geometrical operators and in the dynamics provided by Spin Foams. However, the debate continues as to whether quantum physics should be Barbero-Immirzi parameter dependent. Starting from a discrete SO(4)-BF theory phase space, we find two possible reductions with respect to a discrete form of the simplicity constraints. The first reduces to a phase space with gamma-dependent symplectic structure and more generally in agreement with the phase space underlying Loop Quantum Gravity restricted to a single graph - a.k.a. Twisted Geometries. The second, fuller reduction leads to a gamma-independent symplectic structure on the phase space of piecewise-flat-linear geometries - a.k.a. Regge geometries. Thus, the gamma-dependence of physical predictions is related to the choice of phase space underlying the quantization.

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