Demazure crystals for Kohnert polynomials

Assaf, Sami

doi:10.1090/tran/8560

Demazure crystals for Kohnert polynomials
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by Sami H. Assaf PDF

Trans. Amer. Math. Soc. 375 (2022), 2147-2186

Abstract:

Kohnert polynomials are polynomials indexed by unit cell diagrams in the first quadrant defined earlier by the author and Searles that give a common generalization of Schubert polynomials and Demazure characters for the general linear group. Demazure crystals are certain truncations of normal crystals whose characters are Demazure characters. For each diagram satisfying a southwest condition, we construct a Demazure crystal whose character is the Kohnert polynomial for the given diagram, resolving an earlier conjecture of the author and Searles that these polynomials expand nonnegatively into Demazure characters. We give explicit formulas for the expansions with applications including a characterization of those diagrams for which the corresponding Kohnert polynomial is a single Demazure character.

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