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In this note, we provide a short and self-contained proof that the braid group on n strands acts transitively on the set of reduced factorizations of a Coxeter element in a Coxeter group of finite rank n into products of reflections. We…

Group Theory · Mathematics 2014-02-12 Barbara Baumeister , Matthew Dyer , Christian Stump , Patrick Wegener

Reflection groups, geometry of the discriminant and noncrossing partitions. When W is a well-generated complex reflection group, the noncrossing partition lattice NCP_W of type W is a very rich combinatorial object, extending the notion of…

Group Theory · Mathematics 2010-10-22 Vivien Ripoll

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

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 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 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 real reflection group, two factorizations of a Coxeter element into an arbitrary number of reflections are shown to lie in the same orbit under the Hurwitz action if and only if they use the same multiset of conjugacy classes.…

Combinatorics · Mathematics 2016-12-12 Joel Brewster Lewis , Victor Reiner

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

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 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 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 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

When W is a finite reflection group, the noncrossing partition lattice NCP_W of type W is a rich combinatorial object, extending the notion of noncrossing partitions of an n-gon. A formula (for which the only known proofs are case-by-case)…

Combinatorics · Mathematics 2014-06-10 Vivien Ripoll

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

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

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

In a seminal work, Bessis gave a geometric interpretation of the noncrossing lattice $NC(W)$ associated to a well-generated complex reflection group $W$. Chief component of this was the trivialization theorem, a fundamental correspondence…

Combinatorics · Mathematics 2024-09-16 Theo Douvropoulos

We consider the Hurwitz action on quasipositive factorizations of 3-braids. We prove that every orbit contains an element of a special form. This fact provides an algorithm of finding representatives of every orbit for a given braid. We…

Group Theory · Mathematics 2024-12-03 Stepan Yu. Orevkov

We consider the Hurwitz action on quasipositive factorizations of a 3-braid. In a previous paper, for any given 3-braid we described a certain finite set which contains at least one representative of each orbit. Here we give an algorithm to…

Group Theory · Mathematics 2024-12-04 Stepan Yu. Orevkov

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
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