Double Hurwitz numbers and multisingularity loci in genus 0
Abstract
In the Hurwitz space of rational functions on CP1 with poles of given orders, we study the loci of multisingularities, that is, the loci of functions with a given ramification profile over 0. We prove a recursion relation on the Poincare dual cohomology classes of these loci and deduce a differential equation on Hurwitz numbers.
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