Automorphisms of the Hatcher-Thurston complex

Let S be a compact, connected, orientable surface of positive genus. Let be the Hatcher-Thurston complex of S. We prove that Aut is isomorphic to the extended mapping class group of S modulo its center. The first author is supported by a Rackham Faculty Fellowship, Horace H. Rackham School of Graduate Studies, University of Michigan. The second author is supported in part by the Turkish Academy of Sciences under the Young Scientists Award Program (MK/TüBA-GEBİP 2003-10).