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Forum Mathematicum

Managing Editor: Bruinier, Jan Hendrik

Ed. by Cohen, Frederick R. / Droste, Manfred / Darmon, Henri / Duzaar, Frank / Echterhoff, Siegfried / Gordina, Maria / Neeb, Karl-Hermann / Shahidi, Freydoon / Sogge, Christopher D. / Takayama, Shigeharu / Wienhard, Anna

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Volume 30, Issue 5


The cup product of Brooks quasimorphisms

Michelle Bucher / Nicolas MonodORCID iD: http://orcid.org/0000-0003-1726-4523
Published Online: 2018-02-14 | DOI: https://doi.org/10.1515/forum-2017-0237


We prove the vanishing of the cup product of the bounded cohomology classes associated to any two Brooks quasimorphisms on the free group. This is a consequence of the vanishing of the square of a universal class for tree automorphism groups.

Keywords: Quasimorphism; cup product; free group; bounded cohomology

MSC 2010: 20J06; 20E05; 20J05


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About the article

Received: 2017-11-03

Published Online: 2018-02-14

Published in Print: 2018-09-01

Citation Information: Forum Mathematicum, Volume 30, Issue 5, Pages 1157–1162, ISSN (Online) 1435-5337, ISSN (Print) 0933-7741, DOI: https://doi.org/10.1515/forum-2017-0237.

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