Séminaire Lotharingien de Combinatoire, 93B.34 (2025), 12 pp.

Hyeonjae Choi, Donghyun Kim and Seung Jin Lee

Lusztig q-Weight Multiplicities and KR Crystals

Abstract. Lusztig q-weight multiplicities extend the Kostka-Foulkes polynomials to a broader range of Lie types. In this work, we investigate these multiplicities through the framework of Kirillov-Reshetikhin crystals. Specifically, for type C and type B spin weights, we present a combinatorial formula for Lusztig q-weight multiplicities in terms of energy functions of Kirillov-Reshetikhin crystals, generalizing the charge statistic on semistandard Young tableaux for type A. Additionally, we introduce level-restricted q-weight multiplicities for nonexceptional types, and prove its positivity by providing their combinatorial formulas.


Received: November 15, 2024. Accepted: February 15, 2025. Final version: April 1, 2025.

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