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We give a natural definition of open Hurwitz numbers, where the weight of each ramified covering includes an integer parameter $N$ taken to the power that is equal to the number of boundary components of a Riemann surface with boundary…

Mathematical Physics · Physics 2025-10-10 Alexandr Buryak , Ran J. Tessler , Mikhail Troshkin

In our previous work [CMS24] we defined a new class of enumerative invariants called $k$-leaky double Hurwitz descendants, generalizing both descendant integrals of double ramification cycles and $k$-leaky double Hurwitz numbers. Here, we…

Algebraic Geometry · Mathematics 2025-09-05 Renzo Cavalieri , Hannah Markwig , Johannes Schmitt

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

This is a survey on tropical polytopes from the combinatorial point of view and with a focus on algorithms. Tropical convexity is interesting because it relates a number of combinatorial concepts including ordinary convexity, monomial…

Combinatorics · Mathematics 2008-10-12 Michael Joswig

We study the density of the invariant measure of the Hurwitz complex continued fraction from a computational perspective. It is known that this density is piece-wise real-analytic and so we provide a method for calculating the Taylor…

Number Theory · Mathematics 2018-06-05 Ghaith Hiary , Joseph Vandehey

We discuss two elementary constructions for covers with fixed ramification in positive characteristic. As an application, we compute the number of certain classes of covers between projective lines branched at 4 points and obtain…

Algebraic Geometry · Mathematics 2013-05-24 Irene I. Bouw , Leonardo Zapponi

We introduce new logarithmic Hurwitz spaces $\mathcal{LH}^{\mathbb{Z}_{(p)}}_A$ and $\mathcal{LH}^{\mathbb{F}_{p}}_{A,\Xi}$ over $\mathbb{Z}_{(p)}$ and $\mathbb{F}_p$ respectively that in the mixed characteristic case can be considered as a…

Algebraic Geometry · Mathematics 2026-02-19 Matthias Hippold

We consider ramified coverings of P^1 with arbitrary ramification type over 0 and infinity and simple ramifications elsewhere and prove that the generating function for the numbers of such coverings is a tau-function for the Toda lattice…

Algebraic Geometry · Mathematics 2007-05-23 Andrei Okounkov

Spin Hurwitz numbers count ramified covers of a spin surface, weighted by the size of their automorphism group (like ordinary Hurwitz numbers), but signed $\pm 1$ according to the parity of the covering surface. These numbers were first…

Quantum Algebra · Mathematics 2016-09-21 Sam Gunningham

In this paper, we discuss the properties of the generating functions of spin Hurwitz numbers. In particular, for spin Hurwitz numbers with arbitrary ramification profiles, we construct the weighed sums which are given by Orlov's…

Mathematical Physics · Physics 2023-02-28 Alexander Alexandrov , Sergey Shadrin

We express the topological expansion of the Jacobi Unitary Ensemble in terms of triple monotone Hurwitz numbers. This completes the combinatorial interpretation of the topological expansion of the classical unitary invariant matrix…

Mathematical Physics · Physics 2022-07-27 Massimo Gisonni , Tamara Grava , Giulio Ruzza

In this survey article we give an overview of how noncongruence modular curves can be viewed as Hurwitz moduli spaces of covers of elliptic curves at most branched above the origin. We describe some natural questions that arise, and…

Number Theory · Mathematics 2025-10-15 William Y. Chen

Tropical implicitization means computing the tropicalization of a unirational variety from its parametrization. In the case of a hypersurface, this amounts to finding the Newton polytope of the implicit equation, without computing its…

Algebraic Geometry · Mathematics 2023-06-23 Kemal Rose , Bernd Sturmfels , Simon Telen

We study the irreducible components of special loci of curves whose group of symmetries is given as certain group extension. We introduce some relative Hurwitz data, which we show by using mixed \'etale cohomology theory, identifies some…

Algebraic Geometry · Mathematics 2020-06-22 Benjamin Collas , Sylvain Maugeais

The canonical covering maps from Hurwitz varieties to configuration varieties are important in algebraic geometry. The scheme-theoretic fiber above a rational point is commonly connected, in which case it is the spectrum of a Hurwitz number…

Number Theory · Mathematics 2016-08-31 David P. Roberts

We introduce and develop a language of semigroups over the braid groups for a study of braid monodromy factorizations (bmf's) of plane algebraic curves and other related objects. As an application we give a new proof of Orevkov's theorem on…

Algebraic Geometry · Mathematics 2015-06-26 V. Kharlamov , Vik. S. Kulikov

The construction of hypergeometric 2D Toda $\tau$-functions as generating functions for quantum Hurwitz numbers is extended here to multispecies families. Both the enumerative geometrical significance of these multispecies quantum Hurwitz…

Mathematical Physics · Physics 2016-11-01 J. Harnad

A well-known and difficult problem in computational number theory and algebraic geometry is to write down equations for branched covers of algebraic curves with specified monodromy type. In this article, we present a technique for computing…

Algebraic Geometry · Mathematics 2014-07-07 Simon Rubinstein-Salzedo

We study the asymptotic behaviour of random factorizations of the $n$-cycle into transpositions of fixed genus $g>0$. They have a geometric interpretation as branched covers of the sphere and their enumeration as Hurwitz numbers was…

Probability · Mathematics 2021-05-10 Valentin Féray , Baptiste Louf , Paul Thévenin

In this paper we present an example of a derivation of an ELSV-type formula using the methods of topological recursion. Namely, for orbifold Hurwitz numbers we give a new proof of the spectral curve topological recursion, in the sense of…

Mathematical Physics · Physics 2017-08-22 Petr Dunin-Barkowski , Danilo Lewanski , Alexandr Popolitov , Sergey Shadrin