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Embeddings and the (virtual) cohomological dimension of the braid and mapping class groups of surfaces

Research paper by Daciberg Lima Gonçalves, John Guaschi, Miguel Maldonado

Indexed on: 11 Oct '16Published on: 11 Oct '16Published in: arXiv - Mathematics - Geometric Topology



Abstract

In this paper, we make use of the relations between the braid and mapping class groups of a compact, connected, non-orientable surface N without boundary and those of its orientable double covering S to study embeddings of these groups and their (virtual) cohomological dimensions. We first generalise results of Birman and Chillingworth and of Gon\c{c}alves and Guaschi to show that the mapping class group MCG(N ; k) of N relative to a k-point subset embeds in the mapping class group MCG(S; 2k) of S relative to a 2k-point subset. We then compute the cohomological dimension of the braid groups of all compact, connected aspherical surfaces without boundary. Finally, if the genus of N is greater than or equal to 2, we give upper bounds for the virtual cohomological dimension of MCG(N ; k).