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arXiv 1009.3402gr-qchep-th
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圈量子引力中的多面体

Polyhedra in loop quantum gravity

Eugenio Bianchi, Pietro Dona', Simone Speziale

摘要:

交织物是自旋网络状态的构建块。交织空间是由Kapovich和Millson引入的经典辛流形的量子化。在这里,我们表明,闵可夫斯基定理允许我们解释在这个空间中的一般配置为有界凸多面体在欧几里得空间:多面体是唯一描述的面积和法线,它的脸。我们提供了一个重建的多面体的几何形状:我们给公式的边长,体积和其面的邻接。在量子层面上,这种对应关系使我们能够识别出一个纠缠体与量子多面体的状态,从而推广了圈量子引力文献中熟悉的量子四面体的概念。此外,相干缠绕的结果是在多面体的经典几何上达到顶峰。我们讨论了这一结果与圈量子引力的相关性。特别地,具有任意价的节点的相干自旋网络状态代表半经典多面体的集合。此外,我们还引入了一个度量量子多面体体积的算符,并考察了它与圈量子引力标准体积算符的关系。我们还讨论了具有非单纯图的自旋泡沫的半经典极限。

英文摘要:

Interwiners are the building blocks of spin-network states. The space of intertwiners is the quantization of a classical symplectic manifold introduced by Kapovich and Millson. Here we show that a theorem by Minkowski allows us to interpret generic configurations in this space as bounded convex polyhedra in Euclidean space: a polyhedron is uniquely described by the areas and normals to its faces. We provide a reconstruction of the geometry of the polyhedron: we give formulas for the edge lengths, the volume and the adjacency of its faces. At the quantum level, this correspondence allows us to identify an intertwiner with the state of a quantum polyhedron, thus generalizing the notion of quantum tetrahedron familiar in the loop quantum gravity literature. Moreover, coherent intertwiners result to be peaked on the classical geometry of polyhedra. We discuss the relevance of this result for loop quantum gravity. In particular, coherent spin-network states with nodes of arbitrary valence represent a collection of semiclassical polyhedra. Furthermore, we introduce an operator that measures the volume of a quantum polyhedron and examine its relation with the standard volume operator of loop quantum gravity. We also comment on the semiclassical limit of spinfoams with non-simplicial graphs.

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