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

Mathematical Physics · Physics 2018-06-26 J. Harnad

New theorems characterizing analytically discs in the Euclidean plane $\RR^2$ are proved. Weighted mean value properties of solutions to the modified Helmholtz equation and harmonic functions are used for this purpose. The presence of a…

Analysis of PDEs · Mathematics 2022-09-22 Nikolay Kuznetsov

We construct solutions to the Schwarz boundary value problem on the unit disk and the upper half-plane when the boundary condition is with respect to boundary values in the sense of distributions.

Complex Variables · Mathematics 2023-09-06 William L. Blair

A recurring task in particle physics and statistics is to compute the complex critical points of a product of powers of affine-linear functions. The logarithmic discriminant characterizes exponents for which such a function has a degenerate…

Algebraic Geometry · Mathematics 2025-06-09 Leonie Kayser , Andreas Kretschmer , Simon Telen

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 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

This article is an extended version of preprint math.AG/9902104. We find an explicit formula for the number of topologically different ramified coverings of a sphere by a genus g surface with only one complicated branching point in terms of…

Algebraic Geometry · Mathematics 2009-10-31 T. Ekedahl , S. Lando , M. Shapiro , A. Vainshtein

Hurwitz numbers count genus $g$, degree $d$ covers of the complex projective line with fixed branched locus and fixed ramification data. An equivalent description is given by factorisations in the symmetric group. Simple double Hurwitz…

Combinatorics · Mathematics 2019-04-05 Marvin Anas Hahn

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

Double Hurwitz numbers enumerate branched covers of $\mathbb{CP}^1$ with prescribed ramification over two points and simple ramification elsewhere. In contrast to the single case, their underlying geometry is not well understood. In…

Algebraic Geometry · Mathematics 2023-07-07 Gaëtan Borot , Norman Do , Maksim Karev , Danilo Lewański , Ellena Moskovsky

Branched covers between Riemann surfaces are associated with certain combinatorial data, and Hurwitz existence problem asks whether given data satisfying those combinatorial constraints can be realized by some branched cover. We connect…

Geometric Topology · Mathematics 2020-09-02 Xuwen Zhu

Correlators in topological theories are given by the values of a linear form on the products of operators from a commutative associative algebra (CAA). As a corollary, partition functions of topological theory always satisfy the generalized…

High Energy Physics - Theory · Physics 2015-05-30 A. Mironov , A. Morozov , S. Natanzon

Hurwitz theory provides a large variety of enumerative problems related to algebraic geometry, mathematical physics, and combinatorics. We give a general framework to approach the large genus asymptotics of Hurwitz theory using only…

Algebraic Geometry · Mathematics 2026-04-15 Davide Accadia , Danilo Lewański , Giulio Ruzza

Solutions to optimization problems involving the numerical radius often belong to a special class: the set of matrices having field of values a disk centered at the origin. After illustrating this phenomenon with some examples, we…

Numerical Analysis · Mathematics 2024-12-20 Adrian S. Lewis , Michael L. Overton

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

The radial collapse of a homogeneous disk of collisionless particles can be solved analytically in Newtonian gravitation. To solve the problem in general relativity, however, requires the full machinery of numerical relativity. The collapse…

General Relativity and Quantum Cosmology · Physics 2010-11-01 Andrew M. Abrahams , Stuart L. Shapiro , Saul A. Teukolsky

Simple Hurwitz numbers enumerate branched morphisms between Riemann surfaces with fixed ramification data. In recent years, several variants of this notion for genus $0$ base curves have appeared in the literature. Among them are so-called…

Algebraic Geometry · Mathematics 2022-11-02 Marvin Anas Hahn , Jan-Willem M. van Ittersum , Felix Leid

The aim of this paper is to establish some properties of solutions to the Dirichlet-Neumann problem: $(\partial_z\partial_{\overline{z}})^2 w=g$ in the unit disc $\ID$, $w=\gamma_0$ and…

Complex Variables · Mathematics 2021-03-17 Peijin Li , Qinghong Luo , Saminathan Ponnusamy

Double Hurwitz numbers count branched covers of the projective line with fixed branch points, with simple branching required over all but two points 0 and infinity, and the branching over 0 and infinity specified by partitions of the degree…

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

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