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We study the structures of ordinary simple Hurwitz numbers and monotone Hurwitz numbers with varying genus. More precisely, we prove that when the ramification type is fixed and the genus is treated as a variable, the connected monotone…

Combinatorics · Mathematics 2025-03-05 Chenglang Yang

We consider weighted double Hurwitz numbers, with the weight given by arbitrary rational function times an exponent of the completed cycles. Both special singularities are arbitrary, with the lengths of cycles controlled by formal…

Mathematical Physics · Physics 2025-01-13 Boris Bychkov , Petr Dunin-Barkowski , Maxim Kazarian , Sergey Shadrin

We exhibit a generating function of spin Hurwitz numbers analogous to (disconnected) double Hurwitz numbers that is a tau function of the two-component BKP (2-BKP) hierarchy and is a square root of a tau function of the two-component KP…

Algebraic Geometry · Mathematics 2019-06-24 Junho Lee

We present a study of real Hurwitz numbers enumerating a special kind of real meromorphic functions, which we call simple framed purely real functions. We deduce partial differential equations of cut-and-join type for generating functions…

Algebraic Geometry · Mathematics 2019-02-12 Maxim Kazarian , Sergey Lando , Sergey Natanzon

Hurwitz numbers, which count certain covers of the projective line (or, equivalently, factorizations of permuations into transpositions), have been extensively studied for over a century. The Gromov-Witten potential F of a point, the…

Algebraic Geometry · Mathematics 2007-05-23 Ian Goulden , David Jackson , Ravi Vakil

There is now a renewed interest to the Hurwitz tau-function, counting the isomorphism classes of Belyi pairs, arising in the study of equilateral triangulations and Grothiendicks's dessins d'enfant. It is distinguished by belonging to a…

High Energy Physics - Theory · Physics 2014-11-25 A. Alexandrov , A. Mironov , A. Morozov , S. Natanzon

We derive an algorithm to produce explicit formulas for certain generating functions of double Hurwitz numbers. These formulas generalize a formula of Goulden, Jackson and Vakil for one part double Hurwitz numbers. Immediate consequences…

Combinatorics · Mathematics 2010-08-20 Paul Johnson

In this paper we shall define a special-valued multiple Hurwitz zeta functions, namely the multiple $t$-values $t(\boldsymbol{\alpha})$ and define similarly the multiple star $t$-values as $t^{\star}(\boldsymbol{\alpha})$. Then we consider…

Number Theory · Mathematics 2016-09-07 Chan-Liang Chung

We introduce a new generalization of Stirling numbers of the second kind and analyze their properties, including generating functions, integral representations, and recurrence relations. These numbers are used to approximate Riemann zeta…

Number Theory · Mathematics 2025-10-09 Kamel Mezlini , Tahar Moumni , Najib Ouled Azaiez

This work concerns the semiclassical asymptotics of quantum weighted double Hurwitz numbers. We compute the leading term of the partition function for three versions of the quantum weighted Hurwitz numbers, as well as lower order…

Mathematical Physics · Physics 2016-11-01 J. Harnad , Janosch Ortmann

Classical Hurwitz numbers count branched covers of the Riemann sphere with prescribed ramification data, or equivalently, factorisations in the symmetric group with prescribed cycle structure data. Monotone Hurwitz numbers restrict the…

Geometric Topology · Mathematics 2014-08-19 Norman Do , Alastair Dyer , Daniel V. Mathews

Hurwitz numbers count genus g, degree d covers of the projective line with fixed branch locus. This equals the degree of a natural branch map defined on the Hurwitz space. In tropical geometry, algebraic curves are replaced by certain…

Algebraic Geometry · Mathematics 2010-07-19 Renzo Cavalieri , Paul Johnson , Hannah Markwig

The classical Hurwitz numbers which count coverings of a complex curve have an analog when the curve is endowed with a theta characteristic. These "spin Hurwitz numbers", recently studied by Eskin, Okounkov and Pandharipande, are…

Symplectic Geometry · Mathematics 2012-12-12 Junho Lee , Thomas H. Parker

We derive an explicit formula for the connected $(n,m)$-point functions associated to an arbitrary diagonal tau-function $\tau_f(\boldsymbol{t}^+,\boldsymbol{t}^-)$ of the 2d Toda lattice hierarchy using fermionic computations and the…

Exactly Solvable and Integrable Systems · Physics 2023-11-07 Zhiyuan Wang , Chenglang Yang

We continue our computation, using a combinatorial method based on Gronthendieck's dessins d'enfant, of the number of (weak) equivalence classes of surface branched covers matching certain specific branch data. In this note we concentrate…

Geometric Topology · Mathematics 2018-07-31 Carlo Petronio

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

Hurwitz numbers are a weighted count of degree d ramified covers of curves with specified ramification profiles at marked points on the codomain curve. Isomorphism classes of these covers can be included as a dense open set in a moduli…

Algebraic Geometry · Mathematics 2012-11-13 Brian Katz

The Hurwitz form of a variety is the discriminant that characterizes linear spaces of complementary dimension which intersect the variety in fewer than degree many points. We study computational aspects of the Hurwitz form, relate this to…

Algebraic Geometry · Mathematics 2016-07-20 Bernd Sturmfels

We derive a new explicit formula in terms of sums over graphs for the $n$-point correlation functions of general formal weighted double Hurwitz numbers coming from the Kadomtsev-Petviashvili tau functions of hypergeometric type (also known…

Combinatorics · Mathematics 2022-07-14 Boris Bychkov , Petr Dunin-Barkowski , Maxim Kazarian , Sergey Shadrin

Consequences of the Toda equations arising from the conjectural matrix model for the Riemann sphere are investigated. The Toda equations determine the Gromov-Witten descendent potential (including all genera) of the Riemann sphere from the…

Algebraic Geometry · Mathematics 2007-05-23 R. Pandharipande