Plane Hurwitz Numbers Abstract Jared Ongaro The main objects in this thesis are meromorphic functions obtained as projections to a pencil of lines through a point in P2 . The general goal is to understand how a given a meromorphic function f : X → P1 can be induced from a composition X 99K C → P1 , where C ⊂ P2 is birationally equivalent to the smooth curve X. In particular, it is the desire to characterize meromorphic functions on smooth curves which are obtained in such a way and enumerate such functions. Division of Pure mathematics School of Mathematics University of Nairobi Kenya Email:[email protected] ISBN: 978-91-7447-927-0 It is shown in this thesis that any degree d > 0 meromorphic function on a smooth projective curve C ⊂ P2 of degree d > 4 is isomorphic to a linear projection from a point p ∈ P2 \C to P1 . Further, a planarity filtration of the small Hurwitz space using the minimal degree of a plane curve is introduced such that a given meromorphic function admits such a composition X 99K C → P1 . Additionally, a notion of plane Hurwitz numbers is introduced. ISSN:
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