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This article presents a study of an algebra spanned by the faces of a hyperplane arrangement. The quiver with relations of the algebra is computed and the algebra is shown to be a Koszul algebra. It is shown that the algebra depends only on…

Rings and Algebras · Mathematics 2007-05-23 Franco V. Saliola

The extended weak order on a Coxeter group $W$ is the poset of biclosed sets in its root system. In (Barkley-Speyer 2024), it was shown that when $W=\widetilde{S}_n$ is the affine symmetric group, then the extended weak order is a quotient…

Combinatorics · Mathematics 2025-02-11 Grant T. Barkley

In this paper, we initiate the study of the twisted weak order associated to a twisted Bruhat order for a Coxeter group and explore the relationship between the lattice property of such order and the infinite reduced words. We show that for…

Representation Theory · Mathematics 2018-12-19 Weijia Wang

The weak order is a classical poset structure on a Coxeter group; it is a lattice when the group is finite but merely a meet-semilattice when the group is infinite. Motivated by problems in Kazhdan--Lusztig theory, Matthew Dyer introduced…

Combinatorics · Mathematics 2025-09-03 Grant Barkley , Colin Defant , Patricia Hersh , Jon McCammond , Thomas McConville , David E Speyer

We define a class of partial orders on a Coxeter group associated with sets of reflections. In special cases, these lie between the left weak order and the Bruhat order. We prove that these posets are graded by the length function and that…

Combinatorics · Mathematics 2022-06-28 Angela Carnevale , Matthew Dyer , Paolo Sentinelli

The exchange graph of a 2-acyclic quiver is the graph of mutation-equivalent quivers whose edges correspond to mutations. When the quiver admits a nondegenerate Jacobi-finite potential, the exchange graph admits a natural acyclic…

Representation Theory · Mathematics 2018-04-19 Alexander Garver , Thomas McConville

For a finite dimensional algebra $A$, we establish correspondences between torsion classes and wide subcategories in $mod(A)$. In case $A$ is representation finite, we obtain an explicit bijection between these two classes of subcategories.…

Representation Theory · Mathematics 2017-06-19 Frederik Marks , Jan Stovicek

In this paper, we introduce a new combinatorial operation, called a flip, on arbitrary partially ordered sets. We define a mutation to be a flip that maps a lattice to a lattice. We study properties of flips, and give a necessary and…

Combinatorics · Mathematics 2026-05-12 Kan Nagano

We introduce the concept of a quasiresiduated lattice and prove that every lattice effect algebra can be organized into a commutative quasiresiduated lattice with divisibility. Also conversely, every such a lattice can be converted into a…

Logic · Mathematics 2019-05-15 Ivan Chajda , Helmut Länger

This paper has been withdrawn by the authors due to a crucial computational error. In this paper we deal with the finite case. We prove that a finite bounded ordered set can be represented as the order of principal congruences of a finite…

Rings and Algebras · Mathematics 2013-04-02 G. Grätzer , E. T. Schmidt

We prove that the bounded derived category of the lattice of order ideals of the product of two ordered chains is fractionally Calabi-Yau. We also show that these lattices are derived equivalent to higher Auslander algebras of type A. The…

Representation Theory · Mathematics 2025-09-09 Tal Gottesman

We continue the study on sheaves of rings on finite posets. We present examples where the ring of global sections coincide with toric faces rings, quotients of a polynomial ring by a monomial ideal and algebras with straightening laws. We…

Commutative Algebra · Mathematics 2021-05-18 Morten Brun , Tim Roemer

Let A be a connected hereditary artin algebra. We show that the set of functorially finite torsion classes of A-modules is a lattice if and only if A is either representation-finite (thus a Dynkin algebra) or A has only two simple modules.…

Representation Theory · Mathematics 2014-02-07 Claus Michael Ringel

We study classes of right-angled Coxeter groups with respect to the strong submodel relation of parabolic subgroup. We show that the class of all right-angled Coxeter group is not smooth, and establish some general combinatorial criteria…

Logic · Mathematics 2019-12-19 Tapani Hyttinen , Gianluca Paolini

In [5], Elnitsky constructed three elegant bijections between classes of reduced words for Type $\mathrm{A}$, $\mathrm{B}$ and $\mathrm{D}$ families of Coxeter groups and certain tilings of polygons. This paper offers a particular…

Group Theory · Mathematics 2024-07-23 Robert Nicolaides , Peter Rowley

We prove that finite partial orders with a linear extension form a Ramsey class. Our proof is based on the fact that class of acyclic graphs has the Ramsey property and uses the partite construction.

Combinatorics · Mathematics 2017-03-03 Jaroslav Nešetřil , Vojtěch Rödl

For finite semidistributive lattices the map $\kappa$ gives a bijection between the sets of completely join-irreducible elements and completely meet-irreducible elements. Here we study the $\kappa$-map in the context of torsion classes. It…

Representation Theory · Mathematics 2020-07-17 Emily Barnard , Gordana Todorov , Shijie Zhu

We present a refinement of Ramsey numbers by considering graphs with a partial ordering on their vertices. This is a natural extension of the ordered Ramsey numbers. We formalize situations in which we can use arbitrary families of…

Combinatorics · Mathematics 2016-11-29 Christopher Cox , Derrick Stolee

We develop the basic constructions of homological algebra in the (appropriately defined) unbounded derived categories of modules over algebras over coalgebras over noncommutative rings (which we call semialgebras over corings). We define…

Category Theory · Mathematics 2014-05-12 Leonid Positselski

We investigate the representation of lattices as sublattices of the lattice of all convex subsets (intervals) of a linearly ordered set $(X,\le)$. We introduce the purely lattice-theoretic notion of a \textit{loc-lattice} and prove that…

General Mathematics · Mathematics 2026-03-23 P. Douka , V. Felouzis