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A brief introduction to the theory of ordered sets and lattice theory is given. To illustrate proof techniques in the theory of ordered sets, a generalization of a conjecture of Daykin and Daykin, concerning the structure of posets that can…

Combinatorics · Mathematics 2009-09-25 Jonathan David Farley

We show that the polytopes obtained from the Birkhoff polytope by imposing additional inequalities restricting the "longest increasing subsequence" have Ehrhart quasi-polynomials which are honest polynomials, even though they are just…

Combinatorics · Mathematics 2023-12-21 Per Alexandersson , Sam Hopkins , Gjergji Zaimi

The characterization of lattice polytopes based upon information about their Ehrhart $h^*$-polynomials is a difficult open problem. In this paper, we finish the classification of lattice polytopes whose $h^*$-polynomials satisfy two…

Combinatorics · Mathematics 2015-03-20 Akihiro Higashitani , Benjamin Nill , Akiyoshi Tsuchiya

Stanley's inequalities for partially ordered sets establish important log-concavity relations for sequences of linear extensions counts. Their extremals however, i.e., the equality cases of these inequalities, were until now poorly…

Combinatorics · Mathematics 2023-12-01 Zhao Yu Ma , Yair Shenfeld

A chain poset, by definition, consists of chains of ordered elements in a poset. We study the chain posets associated to two posets: the Boolean algebra and the poset of isotropic flags. We prove that, in both cases, the chain posets…

Combinatorics · Mathematics 2018-02-19 Ian T. Johnson

We define several sorts of mappings on a poset like monotone, strictly monotone, upper cone preserving and variants of these. Our aim is to characterize posets in which some of these mappings coincide. We define special mappings determined…

Combinatorics · Mathematics 2021-03-01 Ivan Chajda , Helmut Länger

We give an explicit combinatorial description of the two-dimensional faces of both the order polytope $\mathcal{O}(P)$ and the chain polytope $\mathcal{C}(P)$ of a partially ordered set $P$. Using these descriptions, we show that for any…

Combinatorics · Mathematics 2025-09-23 Ragnar Freij-Hollanti , Teemu Lundström , Aki Mori

A characteristic polynomial is an important invariant in the field of hyperplane arrangement. For the Linial arrangement of any irreducible root system, Postnikov and Stanley conjectured that all roots of the characteristic polynomial have…

Combinatorics · Mathematics 2020-12-11 Shigetaro Tamura

We study the difference between the number of facets of the order polytope and the chain polytope of a poset. Hibi and Li classified posets where the gap is exactly zero. We describe the bounds on this gap using the new notion of crossing…

Combinatorics · Mathematics 2024-05-29 Binaya Bhandari , Debra Cunningham , Grace Morrell , SuHo Oh , Paxton Smith

In this paper, we study the posets of classes of subgroups of finite group having same set of orders of elements. We show that this poset is a chain only in the case of p-groups and moreover, we characterize all finite groups for which this…

Group Theory · Mathematics 2026-03-09 Sachin Ballal , Tushar Halder

Zonotopes are a rich and fascinating family of polytopes, with connections to many areas of mathematics. In this article we provide a brief survey of classical and recent results related to lattice zonotopes. Our emphasis is on connections…

Combinatorics · Mathematics 2018-08-17 Benjamin Braun , Andrés R. Vindas-Meléndez

We introduce several classes of polytopes contained in $[0,1]^n$ and cut out by inequalities involving sums of consecutive coordinates. We show that the normalized volumes of these polytopes enumerate circular extensions of certain partial…

Combinatorics · Mathematics 2020-07-10 Arvind Ayyer , Matthieu Josuat-Vergès , Sanjay Ramassamy

The Ehrhart polynomial of a lattice polygon P is completely determined by the pair (b(P),i(P)) where b(P) equals the number of lattice points on the boundary and i(P) equals the number of interior lattice points. All possible pairs…

Combinatorics · Mathematics 2020-02-11 Johannes Hofscheier , Benjamin Nill , Dennis Öberg

We present a matrix-theoretic approach for studying and enumerating finite posets through their incidence representations, referred to as poset matrices. Naturally labelled posets are encoded as Boolean lower triangular matrices, allowing a…

Combinatorics · Mathematics 2026-02-05 Gi-Sang Cheon , Hong Joon Choi , Gukwon Kwon , Hojoon Lee , Yaling Wang

The combinatorial mutation $\mathrm{mut}_w(P,F)$ for a lattice polytope $P$ was introduced in the context of mirror symmetry for Fano manifolds in [1]. It was also proved in [1] that for a lattice polytope $P \subseteq N_\mathbb{R}$…

Combinatorics · Mathematics 2020-02-05 Akihiro Higashitani

The Ehrhart polynomial $ehr_P (n)$ of a lattice polytope $P$ gives the number of integer lattice points in the $n$-th dilate of $P$ for all integers $n\geq 0$. The degree of $P$ is defined as the degree of its $h^\ast$-polynomial, a…

Combinatorics · Mathematics 2024-09-24 Matthias Beck , Ellinor Janssen , Katharina Jochemko

We conduct a systematic study of the Ehrhart theory of certain slices of rectangular prisms. Our polytopes are generalizations of the hypersimplex and are contained in the larger class of polypositroids introduced by Lam and Postnikov;…

Combinatorics · Mathematics 2025-04-30 Luis Ferroni , Daniel McGinnis

We extend the notion of chain algebra, originally defined in \cite{GN} for finite distributive lattices, to that of finite pure posets. We show this algebra corresponds to the Ehrhart ring of a (0,1)-polytope, termed the chain polytope, and…

Combinatorics · Mathematics 2025-05-21 Dancheng Lu

The coefficients of the chain polynomial of a finite poset enumerate chains in the poset by their number of elements. The chain polynomials of the partition lattices and their standard type $B$ analogues are shown to have only real roots.…

Combinatorics · Mathematics 2023-01-03 Christos A. Athanasiadis , Katerina Kalampogia-Evangelinou

Let $\mathscr{O}(P)$ and $\mathscr{C}(P)$ denote the order polytope and chain polytope, respectively, associated with a finite poset $P$. We prove the following result: if $P$ is a maximal ranked poset, then the number of triangular…

Combinatorics · Mathematics 2025-03-17 Aki Mori