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Partial permutohedra

Behrend, Roger E. ORCID:, Castillo, Federico, Chavez, Anastasia, Diaz-Lopez, Alexander, Escobar, Laura, Harris, Pamela E. and Insko, Erik 2023. Partial permutohedra. Presented at: 35th Conference on Formal Power Series and Algebraic Combinatorics, 17-21 July 2023. Séminaire Lotharingien de Combinatoire. , vol.89B

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Partial permutohedra are lattice polytopes which were recently introduced and studied by Heuer and Striker [arXiv:2012.09901]. For positive integers m and n, the partial permutohedron P(m,n) is the convex hull of all vectors in {0,1,...,n}^m whose nonzero entries are distinct. We study the face lattice, volume and Ehrhart polynomial of P(m,n), and our methods and results include the following. For any m and n, we obtain a bijection between the nonempty faces of P(m,n) and certain chains of subsets of {1,...,m}, thereby confirming a conjecture of Heuer and Striker. We use this characterization of faces to obtain a closed expression for the h-polynomial of P(m,n). For any m and n with n ≥ m−1, we use a pyramidal subdivision of P(m,n) to establish a recursive formula for the normalized volume of P(m,n), from which we then obtain closed expressions for this volume. We also use a sculpting process (in which P(m,n) is reached by successively removing certain pieces from a simplex or hypercube) to obtain closed expressions for the Ehrhart polynomial of P(m,n) with arbitrary m and fixed n ≤ 3, the volume of P(m,4) with arbitrary m, and the Ehrhart polynomial of P(m,n) with fixed m ≤ 4 and arbitrary n ≥ m−1.

Item Type: Conference or Workshop Item (Paper)
Date Type: Publication
Status: Published
Schools: Mathematics
Subjects: Q Science > QA Mathematics
ISSN: 1286-4889
Funders: Leverhulme Trust
Date of First Compliant Deposit: 13 September 2023
Date of Acceptance: 15 February 2023
Last Modified: 25 Sep 2023 08:49

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