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Billiard arrays and finite-dimensional irreducible \(U_q(\mathfrak{sl}_2)\)-modules. (English) Zbl 1352.17021

Summary: We introduce the notion of a billiard array. This is an equilateral triangular array of one-dimensional subspaces of a vector space \(V\), subject to several conditions that specify which sums are direct. We show that the billiard arrays on \(V\) are in bijection with the 3-tuples of totally opposite flags on \(V\). We classify the billiard arrays up to isomorphism. We use billiard arrays to describe the finite-dimensional irreducible modules for the quantum algebra \(U_q(\mathfrak{sl}_2)\) and the Lie algebra \(\mathfrak{sl}_2\).

MSC:

17B37 Quantum groups (quantized enveloping algebras) and related deformations
15A21 Canonical forms, reductions, classification

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