
Journal of Lie Theory 19 (2009), No. 1, 107148 Copyright Heldermann Verlag 2009 Higher Arf Functions and Moduli Space of Higher Spin Surfaces Sergey Natanzon Moscow State University, Korp. A  Leninske Gory, 11899 Moscow, Russia and: Inst. of Theoretical and Experimental Physics, Independent University of Moscow, Bolshoi Vlasevsky Pereulok 11, 119002 Moscow, Russia natanzon@mccme.ru Anna Pratoussevitch Dept. of Mathematical Sciences, University of Liverpool, Peach Street, Liverpool L69 7ZL, England annap@liv.ac.uk [Abstractpdf] \def\Z{{\Bbb Z}} We describe all connected components of the space of pairs $(P,s)$, where $P$ is a hyperbolic Riemann surface with finitely generated fundamental group and $s$ is an $m$spin structure on $P$. We prove that any connected component is homeomorphic to a quotient of ${\mathbb R}^d$ by a discrete group.\endgraf Our method is based on a description of an $m$spin structure by an $m$Arf function, that is a map $\sigma\colon\pi_1(P,p)\to {\Z}/m{\Z}$ with certain geometric properties. We prove that the set of all $m$Arf functions has a structure of an affine space associated with $H_1(P,{\Z}/m{\Z})$. We describe the orbits of $m$Arf functions under the action of the group of homotopy classes of surface autohomeomorphisms. Natural topological invariants of an orbit are the unordered set of values of the $m$Arf functions on the punctures and the unordered set of values on the $m$Arffunction on the holes. We prove that for $g>1$ the space of $m$Arf functions with prescribed genus and prescribed (unordered) sets of values on punctures and holes is either connected or has two connected components distinguished by the Arf invariant $\delta\in\{0,1\}$. Results for $g=1$ are also given. Keywords: Higher spin surfaces, Arf functions, lifts of Fuchsian groups. MSC: 14J60, 30F10; 14J17, 32S25 [ Fulltextpdf (327 KB)] for subscribers only. 