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The moduli space of \(SU(3)\)-flat connections and the fusion rules. (English) Zbl 0928.58013

As is well-known, the moduli spaces of smooth flat \(G=SU(3)\) connections on the oriented 3-holed 2-sphere \(D\) with fixed holonomies along the three oriented boundary loops can be identified with the spaces \(\mathcal M_{D,\Theta}\), parametrized by \(\Theta\) in a triangular domain in the Lie algebra of a fixed maximal torus of \(G\). The paper studies carefully this identification and discusses the necessary and sufficient conditions for the moduli space to be non-empty. Based on representation theoretical data, the results distinguish only two nontrivial possibilities: either \(\mathcal M_{D,\Theta}\) is homeomorphic to the 2-sphere, or it is one point. Furthermore, the author studies the relationship to the \(\widehat{\mathfrak s\mathfrak l}(3;{\mathbb C})\) fusion rules and thus also the conditions for the non-triviality of the fusion coefficients are described. Finally, the fusion coefficient of a triplet of extremal highest weights equals always one, providing an analog to the classical PRV-conjecture.
Reviewer: Jan Slovák (Brno)

MSC:

58D29 Moduli problems for topological structures
57M05 Fundamental group, presentations, free differential calculus
17B81 Applications of Lie (super)algebras to physics, etc.
17B10 Representations of Lie algebras and Lie superalgebras, algebraic theory (weights)
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