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The intersection data of a hyperplane arrangement is described by a geometric lattice, or equivalently a simple matroid. There is a rich interplay between this combinatorial structure and the topology of the arrangement complement. In this…

Combinatorics · Mathematics 2025-04-22 Christin Bibby

We examine Borel subgroup orbits in the classical symmetric space of type CI, which are parametrized by skew symmetric (n, n)-clans. We describe bijections between such clans, certain weighted lattice paths, and pattern-avoiding signed…

Combinatorics · Mathematics 2020-01-22 Aram Bingham , Ozlem Ugurlu

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

A series of integral lattices parametrised by integers $k,m,n$ are introduced and investigated, where $n$ is the rank of the lattice, including the root lattices described in a uniform way and unimodular lattices such as the Niemeier…

Combinatorics · Mathematics 2024-04-08 Atsushi Matsuo , Hiroki Shimakura

We call a lattice crosscut-simplicial if the crosscut complex of every atomic interval is equal to the boundary of a simplex. Every interval of such a lattice is either contractible or homotopy equivalent to a sphere. Recently, Hersh and…

Combinatorics · Mathematics 2017-09-28 Thomas McConville

An extension of the Tamari lattice to the multiplihedra is discussed, along with projections to the composihedra and the Boolean lattice. The multiplihedra and composihedra are sequences of polytopes that arose in algebraic topology and…

Combinatorics · Mathematics 2015-03-19 Stefan Forcey

In this paper, we continue our study of blade arrangements and the positroidal subdivisions which are induced by them on $\Delta_{k,n}$. A blade is a tropical hypersurface which is generated by a system of $n$ affine simple roots of type…

Combinatorics · Mathematics 2022-10-14 Nick Early

A collection of simple closed curves in $\rr^3$ is called a negative slice if it is the intersection of a flat-at-infinity planar Lagrangian surface and $\{y_2 = a \}$ for some $a < 0$. Examples and non-examples of negative slices are…

Symplectic Geometry · Mathematics 2008-08-11 Phil Eiseman , Jonathan D. Lima , Joshua M. Sabloff , Lisa Traynor

The purpose of the present paper is to give a realization of a cylindric diagram as a subset of root systems of type $A_{\kappa-1}^{(1)}$ and several characterization of its poset structure. Furthermore, the set of order ideals of a…

Combinatorics · Mathematics 2023-02-06 Kento Nakada , Takeshi Suzuki , Yoshitaka Toyosawa

For a partially ordered set P, let Co(P) denote the lattice of all order-convex subsets of P. For a positive integer n, we denote by SUB(LO) (resp., SUB(n)) the class of all lattices that can be embedded into a product of lattices of convex…

General Mathematics · Mathematics 2007-05-23 Marina V. Semenova , Friedrich Wehrung

We define a partial order $\mathcal{P}_n$ on permutations of any given size $n$, which is the image of a natural partial order on inversion sequences. We call this the ``middle order''. We demonstrate that the poset $\mathcal{P}_n$ refines…

Combinatorics · Mathematics 2024-08-30 Mathilde Bouvel , Luca Ferrari , Bridget Eileen Tenner

The lattice of noncrossing partitions is well-known for its wide variety of combinatorial appearances and properties. For example, the lattice is rank-symmetric and enumerated by the Catalan numbers. In this article, we introduce a large…

Combinatorics · Mathematics 2024-09-17 Stella Cohen , Michael Dougherty , Andrew D. Harsh , Spencer Park Martin

The $\gamma$-Cambrian semilattices $\mathcal{C}_{\gamma}$ defined by Reading and Speyer are a family of meet-semilattices associated with a Coxeter group $W$ and a Coxeter element $\gamma\in W$, and they are lattices if and only if $W$ is…

Combinatorics · Mathematics 2015-01-12 Henri Mühle

For a closure space (P,f) with f(\emptyset)=\emptyset, the closures of open subsets of P, called the regular closed subsets, form an ortholattice Reg(P,f), extending the poset Clop(P,f) of all clopen subsets. If (P,f) is a finite convex…

Combinatorics · Mathematics 2013-07-08 Luigi Santocanale , Friedrich Wehrung

A barcode is a finite multiset of intervals on the real line. Jaramillo-Rodriguez (2023) previously defined a map from the space of barcodes with a fixed number of bars to a set of multipermutations, which presented new combinatorial…

Combinatorics · Mathematics 2023-12-15 Alex Bouquet , Andrés R. Vindas-Meléndez

It is known that every relatively pseudocomplemented lattice is residuated and, moreover, it is distributive. Unfortunately, non-distributive lattices with a unary operation satisfying properties similar to relative pseudocomplementation…

Logic · Mathematics 2019-01-23 Ivan Chajda , Helmut Länger

A Lattice is a partially ordered set where both least upper bound and greatest lower bound of any pair of elements are unique and exist within the set. K\"{o}tter and Kschischang proved that codes in the linear lattice can be used for error…

Discrete Mathematics · Computer Science 2021-09-30 Pranab Basu

We survey Jean-Louis Loday's vertex description of the associahedron, and its far reaching influence in combinatorics, discrete geometry and algebra. We present in particular four topics were it plays a central role: lattice congruences of…

Combinatorics · Mathematics 2025-06-09 Vincent Pilaud , Francisco Santos , Günter M. Ziegler

In 2020 Bhavale and Waphare introduced the concept of a nullity of a poset as nullity of its cover graph. According to Bhavale and Waphare, if a dismantlable lattice of nullity k contains r reducible elements then 2 $\leq$ r $\leq$ 2k. In…

Combinatorics · Mathematics 2025-03-18 B. P. Aware , A. N. Bhavale

Birkhoff's representation theorem for finite distributive lattices states that any finite distributive lattice is isomorphic to the lattice of order ideals (lower sets) of the partial order of the join-irreducible elements of the lattice.…

Combinatorics · Mathematics 2026-03-17 Dale R. Worley