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We give uniform formulas for the number of full reflection factorizations of a parabolic quasi-Coxeter element in a Weyl group or complex reflection group, generalizing the formula for the genus-0 Hurwitz numbers. This paper is the…

Combinatorics · Mathematics 2025-05-20 Theo Douvropoulos , Joel Brewster Lewis , Alejandro H. Morales

We prove that two reflection factorizations of a parabolic quasi-Coxeter element in a finite Coxeter group belong to the same Hurwitz orbit if and only if they generate the same subgroup and have the same multiset of conjugacy classes. As a…

Combinatorics · Mathematics 2024-02-07 Theo Douvropoulos , Joel Brewster Lewis

We investigate the so-called dual Matsumoto property or Hurwitz action in finite, affine and arbitrary Coxeter groups. In particular, we want to investigate how to reduce reflection factorizations and how two reflection factorizations of…

Group Theory · Mathematics 2021-10-28 Patrick Wegener , Sophiane Yahiatene

We show that for a parabolic quasi-Coxeter element in an affine Coxeter group the Hurwitz action on its set of reduced factorizations into a product of reflections is transitive. We call an element of the Coxeter group parabolic…

Group Theory · Mathematics 2019-09-27 Patrick Wegener

We enumerate Hurwitz orbits of shortest reflection factorizations of an arbitrary element in the infinite family $G(m, p, n)$ of complex reflection groups. As a consequence, we characterize the elements for which the action is transitive…

Combinatorics · Mathematics 2022-06-17 Joel Brewster Lewis , Jiayuan Wang

Recently, Wang and the second author constructed a bar involution and canonical basis for a quasi-permutation module of the Hecke algebra associated to a type B Weyl group $W$, where the basis is parameterized by left cosets of a…

Representation Theory · Mathematics 2024-07-26 Zachary Carlini , Yaolong Shen

We continue the study of extended Weyl groups $W$, which are reflection groups. Further we recall the definition of a hyperbolic cover of an extended Weyl group, and show that the hyperbolic covers of the extended Weyl groups are extended…

Representation Theory · Mathematics 2025-08-12 Barbara Baumeister , Patrick Wegener , Sophiane Yahiatene

We extend a result of Lewis and Reiner from finite Coxeter groups to all Coxeter groups by showing that two reflection factorizations of a Coxeter element lie in the same Hurwitz orbit if and only if they share the same multiset of…

Combinatorics · Mathematics 2019-01-18 Patrick Wegener , Sophiane Yahiatene

We show that the Hurwitz action is "as transitive as possible" on reflection factorizations of Coxeter elements in the well-generated complex reflection groups $G(d, 1, n)$ (the group of $d$-colored permutations) and $G(d, d, n)$.

Combinatorics · Mathematics 2020-06-29 Joel Brewster Lewis

We show that in the complex reflection group $G_6$, reflection factorizations of a Coxeter element that have the same length and multiset of conjugacy classes are in the same Hurwitz orbit. This confirms one case of a conjecture of Lewis…

Combinatorics · Mathematics 2022-02-07 Gaurav Gawankar , Dounia Lazreq , Mehr Rai , Seth Sabar

For any Coxeter group W, we define a filtration of H^*(W;ZW) by W-submodules and then compute the associated graded terms. More generally, if U is a CW complex on which W acts as a reflection group we compute the associated graded terms for…

Group Theory · Mathematics 2009-04-23 Michael W Davis , Jan Dymara , Tadeusz Januszkiewicz , Boris Okun

We provide a necessary and sufficient condition on an element of a finite Coxeter group to ensure the transitivity of the Hurwitz action on its set of reduced decompositions into products of reflections. We show that this action is…

Group Theory · Mathematics 2015-12-16 Barbara Baumeister , Thomas Gobet , Kieran Roberts , Patrick Wegener

The classical Hurwitz numbers count the fixed-length transitive transposition factorizations of a permutation, with a remarkable product formula for the case of minimum length (genus $0$). We study the analogue of these numbers for…

Combinatorics · Mathematics 2022-06-17 Theo Douvropoulos , Joel Brewster Lewis , Alejandro H. Morales

We enumerate factorizations of a Coxeter element in a well generated complex reflection group into arbitrary factors, keeping track of the fixed space dimension of each factor. In the infinite families of generalized permutations, our…

Combinatorics · Mathematics 2024-02-07 Joel Brewster Lewis , Alejandro H. Morales

We prove that the Hurwitz action on reflection factorizations of Coxeter elements is transitive up to certain natural constraints in the complex reflection groups G4 and G5. This affirms a more general conjecture by Lewis and Reiner in…

Combinatorics · Mathematics 2018-08-06 Zachery Peterson

In a finite Coxeter group $W$ and with two given conjugacy classes of parabolic subgroups $[X]$ and $[Y]$, we count those parabolic subgroups of $W$ in $[Y]$ that are full support, while simultaneously being simple extensions (i.e.,…

Combinatorics · Mathematics 2022-09-14 Theo Douvropoulos

Given an irreducible well-generated complex reflection group W with Coxeter number h, we call a Coxeter element any regular element (in the sense of Springer) of order h in W; this is a slight extension of the most common notion of Coxeter…

Combinatorics · Mathematics 2014-12-16 Victor Reiner , Vivien Ripoll , Christian Stump

In this paper, we study $k$-parabolic arrangements, a generalization of $k$-equal arrangements for finite real reflection groups. When $k=2$, these arrangements correspond to the well-studied Coxeter arrangements. Brieskorn (1971) showed…

Combinatorics · Mathematics 2009-09-04 Hélène Barcelo , Christopher Severs , Jacob A. White

Let $W$ be an arbitrary Coxeter group, possibly of infinite rank. We describe a decomposition of the centralizer $Z_W(W_I)$ of an arbitrary parabolic subgroup $W_I$ into the center of $W_I$, a Coxeter group and a subgroup defined by a…

Group Theory · Mathematics 2012-01-10 Koji Nuida

Parabolic subgroups $W_I$ of Coxeter systems $(W,S)$, as well as their ordinary and double quotients $W / W_I$ and $W_I \backslash W / W_J$, appear in many contexts in combinatorics and Lie theory, including the geometry and topology of…

Combinatorics · Mathematics 2017-12-15 Sara C. Billey , Matjaž Konvalinka , T. Kyle Petersen , William Slofstra , Bridget E. Tenner
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