Duke Mathematical Journal

Homology of the curve complex and the Steinberg module of the mapping class group

Nathan Broaddus

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By the work of Harer, the reduced homology of the complex of curves is a fundamental cohomological object associated to all torsion-free finite index subgroups of the mapping class group. We call this homology group the Steinberg module of the mapping class group. It was previously proved that the curve complex has the homotopy type of a bouquet of spheres. Here, we give the first explicit homologically nontrivial sphere in the curve complex and show that under the action of the mapping class group, the orbit of this homology class generates the reduced homology of the curve complex.

Article information

Duke Math. J., Volume 161, Number 10 (2012), 1943-1969.

First available in Project Euclid: 27 June 2012

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Mathematical Reviews number (MathSciNet)

Zentralblatt MATH identifier

Primary: 57N05: Topology of $E^2$ , 2-manifolds
Secondary: 32G15: Moduli of Riemann surfaces, Teichmüller theory [See also 14H15, 30Fxx]


Broaddus, Nathan. Homology of the curve complex and the Steinberg module of the mapping class group. Duke Math. J. 161 (2012), no. 10, 1943--1969. doi:10.1215/00127094-1645634. https://projecteuclid.org/euclid.dmj/1340801628

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