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We are building a theory of simple Hurwitz numbers for the reflection groups B and D parallel to the classical theory for the symmetric group. We also study analogs of the cut-and-join operators. An algebraic description of Hurwitz numbers…

Combinatorics · Mathematics 2023-03-20 Raphaël Fesler

In this paper, we introduce a kind of decomposition of a finite group called a uniform group factorization, as a generalization of exact factorizations of a finite group. A group $G$ is said to admit a uniform group factorization if there…

Group Theory · Mathematics 2023-11-16 Kazuki Kanai , Kengo Miyamoto , Koji Nuida , Kazumasa Shinagawa

We classify all spherical 2-designs that arise as orbits of finite group actions on real inner product spaces. Although it is well known that such designs can occur in representations without trivial components, we give a complete…

Combinatorics · Mathematics 2025-08-19 Kuan-Cheng Chien , Ming-Hsuan Kang

A proof of Lagrange's and Jacobi's four-square theorem due to Hurwitz utilizes orders in a quaternion algebra over the rationals. Seeking a generalization of this technique to orders over number fields, we identify two key components: an…

Number Theory · Mathematics 2025-09-25 Matěj Doležálek

A factorization of the inverse of a Hermetian positive definite matrix based on a diagonal by diagonal recurrence formulae permits the inversion of Block Toeplitz matrices, using only matrix-vector products, and with a complexity of…

Spectral Theory · Mathematics 2007-05-23 Rami Kanhouche

We discuss an interesting duality known to occur for certain complex reflection groups, namely the duality groups. Our main construction yields a concrete, representation theoretic realisation of this duality. This allows us to naturally…

Rings and Algebras · Mathematics 2020-07-20 Benjamin Briggs

We show that the Hausdorff reflection preserves the shape type of spaces. Some examples as well as the applicability in inverse limits of finite spaces are presented.

General Topology · Mathematics 2024-12-11 Diego Mondéjar

We introduce a new renormalization procedure on double rotations, which is reminiscent of the classical Rauzy induction. Using this renormalization we prove that the set of parameters which induce infinite type double rotations has…

Dynamical Systems · Mathematics 2021-02-24 Mauro Artigiani , Charles Fougeron , Pascal Hubert , Alexandra Skripchenko

We consider the three body problem on $S^1$ under the cotangent potential. We first construct homothetic orbits ending in singularities, including total collision singularity and collision-antipodal singularity. Then certain symmetrical…

Dynamical Systems · Mathematics 2023-01-03 Shuqiang Zhu

It is often assumed that a warped galaxy can be modeled by a set of rings. This paper verifies numerically the validity of this assumption by the study of periodic orbits populating a heavy self-gravitating warped disk. The phase space…

Astrophysics · Physics 2009-11-06 Y. Revaz , D. Pfenniger

This paper show that two doubly infinite series generate a totally nonnegative Hurwitz-type matrix if and only if their ratio represents an S-functions of a certain kind. The doubly infinite case needs a specific approach, since the ratios…

Complex Variables · Mathematics 2016-09-29 Alexander Dyachenko

We give formulae for the cumulants of complex Wishart (LUE) and inverse Wishart matrices (inverse LUE). Their large-$N$ expansions are generating functions of double (strictly and weakly) monotone Hurwitz numbers which count constrained…

Mathematical Physics · Physics 2021-04-12 Fabio Deelan Cunden , Antoine Dahlqvist , Neil O'Connell

Hurwitz numbers count branched covers of the sphere and have been of interest in various fields of mathematics. Motivated by the Matching-Jack conjecture of Goulden and Jackson, Chapuy and Do\l\k{e}ga recently introduced a notion of…

Combinatorics · Mathematics 2023-12-19 Valentin Bonzom , Victor Nador

We develop a mutation theory for quivers with oriented 2-cycles using a structure called a homotopy, defined as a normal subgroupoid of the quiver's fundamental groupoid. This framework extends Fomin-Zelevinsky mutations of 2-acyclic…

Combinatorics · Mathematics 2026-01-07 Fang Li , Siyang Liu , Lang Mou , Jie Pan

In this paper, we collect a number of facts about double Hurwitz numbers, where the simple branch points are replaced by their more general analogues --- completed (r+1)-cycles. In particular, we give a geometric interpretation of these…

Combinatorics · Mathematics 2014-02-26 S. Shadrin , L. Spitz , D. Zvonkine

The properties common to the Lorenz and Chen attractors, as well as their fundamental differences, have been studied for many years in a vast number of works and remain a topic far from a rigorous and complete description. In this paper we…

Dynamical Systems · Mathematics 2025-12-12 Vladimir N. Belykh , Nikita V. Barabash , Anastasia E. Suroegina

We take a direct approach to computing the orbits for the action of the automorphism group $\mathbb{G}_2$ of the Honda formal group law of height $2$ on the associated Lubin-Tate rings $R_2$. We prove that $(R_2/p)_{\mathbb{G}_2} \cong…

Algebraic Topology · Mathematics 2018-12-24 Agnes Beaudry , Naiche Downey , Connor McCranie , Luke Meszar , Andy Riddle , Peter Rock

Going beyond the studies of single and double Hurwitz numbers, we report some progress towards studying Hurwitz numbers which correspond to ramified coverings of the Riemann sphere involving three nonsimple branch points. We first prove a…

Combinatorics · Mathematics 2024-07-24 Ricky Xiao-Feng Chen

Double Hurwitz numbers have at least four equivalent definitions. Most naturally, they count covers of the Riemann sphere by genus g curves with certain specified ramification data. This is classically equivalent to counting certain…

Algebraic Geometry · Mathematics 2013-03-08 Paul Johnson

We study a simple analytic solution to Einstein's field equations describing a thin spherical shell consisting of collisionless particles in circular orbit. We then apply two independent criteria for the identification of circular orbits,…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Monica L. Skoge , Thomas W. Baumgarte