Grounded partitions of type $A_1^{(1)}$ at levels 1 and 2: bijections, affine crystal graphs, and partition identities

Fuente: arXiv
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Autores principales: Dombos, Benedek, Jang, Jihyeug
Formato: Preprint
Publicado: 2025
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author Dombos, Benedek
Jang, Jihyeug
author_facet Dombos, Benedek
Jang, Jihyeug
contents Grounded partitions, introduced by Dousse and Konan, are coloured partitions satisfying difference conditions given by a matrix with nonnegative integer entries. For the matrices studied in this paper, the generating functions are known to be infinite products, corresponding to the principal specialisation of characters of highest weight modules of type $A_1^{(1)}$. We give the first bijective proof that the generating functions of grounded partitions at level $2$ are infinite products. We then give a new combinatorial model for affine crystal graphs of type $A_1^{(1)}$ at level $2$, where the vertices are grounded partitions and the arrows are given by explicit bracketing rules. The grounded partition model for affine crystal graphs of highest weights $Λ_0$, $Λ_1$ and $Λ_0 + Λ_1$ gives rise to new $q$-series identities obtained by decomposing the affine crystal graphs into the crystal graphs of finite type $A_1$ via the restricted representation.
format Preprint
id arxiv_https___arxiv_org_abs_2508_02664
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Grounded partitions of type $A_1^{(1)}$ at levels 1 and 2: bijections, affine crystal graphs, and partition identities
Dombos, Benedek
Jang, Jihyeug
Combinatorics
Representation Theory
Grounded partitions, introduced by Dousse and Konan, are coloured partitions satisfying difference conditions given by a matrix with nonnegative integer entries. For the matrices studied in this paper, the generating functions are known to be infinite products, corresponding to the principal specialisation of characters of highest weight modules of type $A_1^{(1)}$. We give the first bijective proof that the generating functions of grounded partitions at level $2$ are infinite products. We then give a new combinatorial model for affine crystal graphs of type $A_1^{(1)}$ at level $2$, where the vertices are grounded partitions and the arrows are given by explicit bracketing rules. The grounded partition model for affine crystal graphs of highest weights $Λ_0$, $Λ_1$ and $Λ_0 + Λ_1$ gives rise to new $q$-series identities obtained by decomposing the affine crystal graphs into the crystal graphs of finite type $A_1$ via the restricted representation.
title Grounded partitions of type $A_1^{(1)}$ at levels 1 and 2: bijections, affine crystal graphs, and partition identities
topic Combinatorics
Representation Theory
url https://arxiv.org/abs/2508.02664