Area Operator in Loop Quantum Gravity

Abstract

A hyperlink is a finite set of non-intersecting simple closed curves in $\mathbb{R}\times {\mathbb{R}}^3$. Let $S$ be an orientable surface in ${\mathbb{R}}^3$. The dynamical variables in General Relativity are the vierbein $e$ and a $\mathfrak{su}(2)\times \mathfrak{su}(2)$-valued connection $\omega$. Together with Minkowski metric, $e$ will define a metric $g$ on the manifold. Denote $A_S(e)$ as the area of $S$, for a given choice of $e$. The Einstein-Hilbert action $S(e,\omega )$ is defined on $e$ and $\omega$. We will quantize the area of the surface $S$ by integrating $A_S(e)$ against a holonomy operator of a hyperlink $L$, disjoint from $S$, and the exponential of the Einstein-Hilbert action, over the space of vierbeins $e$ and $\mathfrak{su}(2)\times \mathfrak{su}(2)$-valued connections $\omega$. Using our earlier work done on Chern-Simons path integrals in ${\mathbb{R}}^3$, we will write this infinite dimensional path integral as the limit of a sequence of Chern-Simons integrals. Our main result shows that the area operator can be computed from a link-surface diagram between $L$ and $S$. By assigning an irreducible representation of $\mathfrak{su}(2)\times \mathfrak{su}(2)$ to each component of $L$, the area operator gives the total net momentum impact on the surface $S$.

arXiv admin note: text overlap with arXiv:1701.04397, arXiv:1705.00396

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