Extended mapping class group

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Definition

Suppose X is a locally connected locally compact Hausdorff space. The extended mapping class group of X, denoted MCG*(X), is defined as the zeroth homeotopy group of X.

Explicitly, it is defined as follows: let Homeo(X) denote the self-homeomorphism group of X, viewed as a topological space with the compact-open topology. With this topology, it becomes a T0 topological group (see here). We define:

MCG*(X)=π0(Homeo(X),identity map)=Homeo(X)/(Path component of identity in Homeo(X))