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A non-Levi branching rule in terms of Littelmann paths. (English) Zbl 1436.22003

Summary: We prove a conjecture of Naito-Sagaki about a branching rule for the restriction of irreducible representations of \(\mathfrak{sl}(2n,\mathbb{C})\) to \(\mathfrak{sp}(2n,\mathbb{C})\). The conjecture is in terms of certain Littelmann paths, with the embedding given by the folding of the type \(A_{2n-1}\) Dynkin diagram. So far, the only known non-Levi branching rules in terms of Littelmann paths are the diagonal embeddings of Lie algebras in their product yielding the tensor product multiplicities.

MSC:

22E25 Nilpotent and solvable Lie groups
05E05 Symmetric functions and generalizations
05E10 Combinatorial aspects of representation theory
20G05 Representation theory for linear algebraic groups
22E55 Representations of Lie and linear algebraic groups over global fields and adèle rings

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