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We introduce bijections between generalized type $A_n$ noncrossing partitions (that is, associated to arbitrary standard Coxeter elements) and fully commutative elements of the same type. The latter index the diagram basis of the classical…

Combinatorics · Mathematics 2016-08-17 Thomas Gobet

Let $(W,S)$ be a Coxeter system, and write $S=\{s_i:i\in I\}$, where $I$ is a finite index set. Fix a nonempty convex subset $\mathscr{L}$ of $W$. If $W$ is of type $A$, then $\mathscr{L}$ is the set of linear extensions of a poset, and…

Combinatorics · Mathematics 2025-05-06 Grant Barkley , Colin Defant , Eliot Hodges , Noah Kravitz , Mitchell Lee

The star operation, originally introduced by Kazhdan and Lusztig, was later specialized by Ernst to the so-called weak star reduction on the set of fully commutative elements of a Coxeter group. In this paper, we classify the star and weak…

Combinatorics · Mathematics 2025-08-13 Riccardo Biagioli , Luca Costantini , Elisa Sasso

We study the quiver of the descent algebra of a finite Coxeter group W. The results include a derivation of the quiver of the descent algebra of types A and B. Our approach is to study the descent algebra as an algebra constructed from the…

Representation Theory · Mathematics 2008-07-09 Franco V. Saliola

For any finite Coxeter group W, we introduce two new objects: its cutting poset and its biHecke monoid. The cutting poset, constructed using a generalization of the notion of blocks in permutation matrices, almost forms a lattice on W. The…

Combinatorics · Mathematics 2013-10-08 Florent Hivert , Anne Schilling , Nicolas M. Thiéry

Let $(W, I)$ be a finite Coxeter group. In the case where $W$ is a Weyl group, Berenstein and Kazhdan in \cite{BK} constructed a monoid structure on the set of all subsets of $I$ using unipotent $\chi$-linear bicrystals. In this paper, we…

Group Theory · Mathematics 2009-04-14 Xuhua He

We prove that a non-spherical irreducible Coxeter group is (directly) indecomposable and that a non-spherical and non-affine Coxeter group is strongly indecomposable in the sense that all its finite index subgroups are (directly)…

Group Theory · Mathematics 2007-05-23 Luis Paris

In this paper we investigate the endomorphism algebras of standard cluster tilting objects in the stably 2-Calabi-Yau categories $\Sub{\Lambda_w}$ with elements $w$ in Coxeter groups in \cite{BIRSc}. They are examples of the 2-Auslander…

Representation Theory · Mathematics 2012-10-30 Osamu Iyama , Idun Reiten

We study the cohomology with modular coefficients of Deligne-Lusztig varieties associated to Coxeter elements. Under some torsion-free assumption on the cohomology we derive several results on the principal l-block of a finite reductive…

Representation Theory · Mathematics 2012-04-11 Olivier Dudas

In [APS], the authors characterize the partitions of $n$ whose corresponding representations of $S_n$ have nontrivial determinant. The present paper extends this work to all irreducible finite Coxeter groups $W$. Namely, given a nontrivial…

Representation Theory · Mathematics 2017-10-10 Debarun Ghosh , Steven Spallone

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

We define for every affine Coxeter graph a certain factor group of the associated Artin group and prove that some of these groups appear as orbifold fundamental groups of moduli spaces. Examples are the moduli space of nonsingular cubic…

Algebraic Geometry · Mathematics 2007-06-13 Eduard Looijenga

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

The exact-sequence structure behind the Arnold--Douglas--Gupta family of higher-order mixed finite elements for plane elasticity on barycentric refinements is made explicit. On each macro triangle, the symmetric stress space is obtained by…

Numerical Analysis · Mathematics 2026-04-30 Chunyu Chen , Long Chen , Xuehai Huang

Brauer and Fowler noted restrictions on the structure of a finite group G in terms of the order of the centralizer of an involution t in G. We consider variants of these themes. We first note that for an arbitrary finite group G of even…

Group Theory · Mathematics 2018-08-16 Robert M. Guralnick , Geoffrey R. Robinson

We prove universal (case-free) formulas for the weighted enumeration of factorizations of Coxeter elements into products of reflections valid in any well-generated reflection group $W$, in terms of the spectrum of an associated operator,…

Combinatorics · Mathematics 2023-06-14 Guillaume Chapuy , Theo Douvropoulos

The normalizer $N_W(W_J)$ of a standard parabolic subgroup $W_J$ of a finite Coxeter group $W$ splits over the parabolic subgroup with complement $N_J$ consisting of certain minimal length coset representatives of $W_J$ in $W$. In this note…

Group Theory · Mathematics 2011-02-14 Matjaž Konvalinka , Götz Pfeiffer , Claas Röver

In one of his papers on the weak order of Coxeter groups, Dyer formulates several conjectures. Among these, one affirms that the extended weak order forms a lattice, while another offers an algebraic-geometric description of the join of two…

Combinatorics · Mathematics 2026-05-13 Riccardo Biagioli , Lorenzo Perrone

We extend properties of the weak order on finite Coxeter groups to Weyl groupoids admitting a finite root system. In particular, we determine the topological structure of intervals with respect to weak order, and show that the set of…

Quantum Algebra · Mathematics 2010-03-17 Istvan Heckenberger , Volkmar Welker

Let W be an irreducible, finitely generated Coxeter group. The geometric representation provides an discrete embedding in the orthogonal group of the so-called Tits form. One can look at the representation modulo the kernel of this form; we…

Group Theory · Mathematics 2012-11-27 Yves de Cornulier