International Mathematics Research Notices Advance Access published online on January 21, 2009
International Mathematics Research Notices, doi:10.1093/imrn/rnn164
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Lefschetz Fibrations and an Invariant of Finitely Presented Groups
Department of Mathematics, Middle East Technical University, 06531 Ankara, Turkey
Correspondence: Correspondence to be sent to: korkmaz{at}metu.edu.tr
Every finitely presented group is the fundamental group of the total space of a Lefschetz fibration. This follows from results of Gompf and Donaldson, and was also proved by Amoros–Bogomolov–Katzarkov–Pantev. We give another proof by providing the monodromy explicitly. We then define the genus of a finitely presented group
to be the minimal genus of a Lefschetz fibration with fundamental group
. We also give some estimates of the genus of certain groups.