Seminar in Real and Complex Geometry

Thursday, January 12, 2023, 16:15-17:45, Ornstein 111 and online via zoom




Boris Bychkov
(Haifa University)

Topological recursion for generalized double Hurwitz numbers


Abstract
             

Topological recursion is a remarkable universal recursive procedure that has been found in many enumerative geometry problems, from combinatorics of maps, to random matrices, Gromov-Witten invariants, Hurwitz numbers, Mirzakhani's hyperbolic volumes of moduli spaces, knot polynomials. A recursion needs an initial data: a spectral curve, and the recursion defines the sequence of invariants of that spectral curve. In the talk I will define the topological recursion, spectral curves and their invariants, and illustrate it with examples; I will introduce the Fock space formalism which proved to be very efficient for computing TR-invariants for the various classes of Hurwitz-type numbers and I will describe our results on explicit closed algebraic formulas for generating functions of generalized double Hurwitz numbers, and how this allows to prove topological recursion for a wide class of problems. If time permits I'll talk about the implications for the so-called ELSV-type formulas (relating Hurwitz-type numbers to intersection numbers on the moduli spaces of algebraic curves); in particular, I'll explain how this almost immediately gives proofs (of a purely combinatorial-algebraic nature) of the original ELSV formula and of its r-spin generalization (originally conjectured by D.Zvonkine). The talk is based on the series of joint works with P. Dunin-Barkowski, M. Kazarian and S. Shadrin.