SECTIONS OF SURFACE BUNDLES AND LEFSCHETZ FIBRATIONS

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2013-11-01
Baykur, R. Inanc
Korkmaz, Mustafa
Monden, Naoyuki
We investigate the possible self-intersection numbers for sections of surface bundles and Lefschetz fibrations over surfaces. When the fiber genus g and the base genus h are positive, we prove that the adjunction bound 2h-2 is the only universal bound on the self-intersection number of a section of any such genus g bundle and fibration. As a side result, in the mapping class group of a surface with boundary, we calculate the precise value of the commutator lengths of all powers of a Dehn twist about a boundary component, concluding that the stable commutator length of such a Dehn twist is 1/2. We furthermore prove that there is no upper bound on the number of critical points of genus-g Lefschetz fibrations over surfaces with positive genera admitting sections of maximal self-intersection, for g >= 2.
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY

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Citation Formats
R. I. Baykur, M. Korkmaz, and N. Monden, “SECTIONS OF SURFACE BUNDLES AND LEFSCHETZ FIBRATIONS,” TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY, pp. 5999–6016, 2013, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/48554.