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Journal of Algebraic Combinatorics

, Volume 27, Issue 3, pp 263–273 | Cite as

Degrees of stretched Kostka coefficients

  • Tyrrell B. McAllister
Open Access
Article

Abstract

Given a partition λ and a composition β, the stretched Kostka coefficient \(\mathcal {K}_{\lambda \beta}(n)\) is the map n K n λ,n β sending each positive integer n to the Kostka coefficient indexed by n λ and n β. Kirillov and Reshetikhin (J. Soviet Math. 41(2), 925–955, 1988) have shown that stretched Kostka coefficients are polynomial functions of n. King, Tollu, and Toumazet have conjectured that these polynomials always have nonnegative coefficients (CRM Proc. Lecture Notes 34, 99–112, 2004), and they have given a conjectural expression for their degrees (Séminaire Lotharingien de Combinatoire 54A, 2006).

We prove the values conjectured by King, Tollu, and Toumazet for the degrees of stretched Kostka coefficients. Our proof depends upon the polyhedral geometry of Gelfand–Tsetlin polytopes and uses tilings of GT-patterns, a combinatorial structure introduced in De Loera and McAllister, (Discret. Comput. Geom. 32(4), 459–470, 2004).

Keywords

Kostka coefficient Representation theory Gelfand–Tsetlin polytope 

Mathematics Subject Classification (2000)

17B10 52B12 

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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  1. 1.Department of Mathematics and Computer ScienceEindhoven University of TechnologyEindhovenThe Netherlands

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