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We define a new class of enumerative invariants called $k$-leaky double Hurwitz descendants, generalizing both descendant integrals of double ramification cycles and the $k$-leaky double Hurwitz numbers introduced in previous work of…

Algebraic Geometry · Mathematics 2024-04-17 Renzo Cavalieri , Hannah Markwig , Johannes Schmitt

We introduce $(r+1)$-completed cycles $k$-leaky Hurwitz numbers and prove piecewise polynomiality as well as establishing their chamber polynomiality structure and their wall crossing formulae. For $k=0$ the results recover previous results…

Combinatorics · Mathematics 2025-11-27 Davide Accadia , Maksim Karev , Danilo Lewański

In recent work, the authors derived a tropical interpretation of monotone and strictly monotone double Hurwitz numbers. In this paper, we apply the technique of tropical flows to this interpretation in order to provide a new proof of the…

Algebraic Geometry · Mathematics 2019-05-08 Marvin Anas Hahn , Danilo Lewanski

We extract a system of numerical invariants from logarithmic intersection theory on pluricanonical double ramification cycles, and show that these invariants exhibit a number of properties that are enjoyed by double Hurwitz numbers. Among…

Algebraic Geometry · Mathematics 2025-05-12 Renzo Cavalieri , Hannah Markwig , Dhruv Ranganathan

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

Hurwitz numbers enumerate branched morphisms between Riemannn surfaces with fixed numerical data. They represent important objects in enumerative geometry that are accessible by combinatorial techniques. In the past decade, many variants of…

Combinatorics · Mathematics 2023-10-10 Sean Gearoid Fitzgerald , Marvin Anas Hahn , Síofra Kelly

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

Hurwitz numbers count covers of curves satisfying fixed ramification data. Via monodromy representation, this counting problem can be transformed to a problem of counting factorizations in the symmetric group. This and other beautiful…

Combinatorics · Mathematics 2023-12-07 Marvin Anas Hahn , Hannah Markwig

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

Weighted Hurwitz numbers arise as coefficients in the power sum expansion of deformed hypergeometric $\tau$--functions. They specialise to essentially all known cases of Hurwitz numbers, including classical, monotone, strictly monotone and…

Combinatorics · Mathematics 2025-11-04 Marvin Anas Hahn , Brian O'Callaghan , Jonas Wahl

We study rational double Hurwitz cycles, i.e. loci of marked rational stable curves admitting a map to the projective line with assigned ramification profiles over two fixed branch points. Generalizing the phenomenon observed for double…

Algebraic Geometry · Mathematics 2013-05-21 Aaron Bertram , Renzo Cavalieri , Hannah Markwig

Single Hurwitz numbers enumerate branched covers of the Riemann sphere with specified genus, prescribed ramification over infinity, and simple branching elsewhere. They exhibit a remarkably rich structure. In particular, they arise as…

Geometric Topology · Mathematics 2018-11-14 Norman Do , Maksim Karev

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

Hurwitz numbers enumerate branched morphisms between Riemann surfaces. For a fixed elliptic target, Hurwitz numbers are intimately related to mirror symmetry following work of Dijkgraaf. In recent work of Chapuy and Dolega a new variant of…

Combinatorics · Mathematics 2024-10-28 Marvin Anas Hahn , Hannah Markwig

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 analyze a new family of weighted double Hurwitz numbers that was introduced as a notable example in the context of the $x-y$ duality for logarithmic topological recursion. We use this family to systematically demonstrate, refine and…

Algebraic Geometry · Mathematics 2026-05-19 Alexander Alexandrov , Boris Bychkov , Petr Dunin-Barkowski , Maxim Kazarian , Sergey Shadrin

We study properties of the tropical double Hurwitz loci defined by Bertram, Cavalieri and Markwig. We show that all such loci are connected in codimension one. If we mark preimages of simple ramification points, then for a generic choice of…

Algebraic Geometry · Mathematics 2015-12-02 Simon Hampe

Multiparametric families of hypergeometric $\tau$-functions of KP or Toda type serve as generating functions for weighted Hurwitz numbers, providing weighted enumerations of branched covers of the Riemann sphere. A graphical interpretation…

Mathematical Physics · Physics 2019-07-02 A. Alexandrov , G. Chapuy , B. Eynard , J. Harnad

Hurwitz numbers with completed cycles are standard Hurwitz numbers with simple branch points replaced by completed cycles. In fact, simple branch points correspond to completed $2$-cycles. Okounkov and Pandharipande have established the…

Combinatorics · Mathematics 2023-11-14 Ricky X. F. Chen , Zhen-Ran Wang

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
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