Suppose $G$ a finitely generated nilpotent topological group and we consider its rationalization $G_\mathbb{Q}$. This space may fail to be a topological group, but it's always a group-like H-space.

We know that for rationalization of groups maps of the form $x\to x^n$ are bijections. My question is: can we determine if $G$ is rational (as topological space) by the maps of the above form? For example is this theorem correct?

Theorem: A topological group $G$ is rational, that is $G$ is homotopy equivalent to $G_\mathbb{Q}$, iff all the maps $x\to x^n$ are homotopy equivalences.


1 Answer 1


Yes, since the group power map induces multiplication by $n$ on homotopy groups, turning them into rational vector spaces.


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