Given a topological group G, we can think of the space ofhomomorphisms $\hom(\mathbb{Z}^n, G)$ as the space of
$n$-tuples of elements of $G$ that commute pairwise. These spaces are more subtle than one might think, and even basic
invariants such as the number of connected components can lead to surprising results. Fixing $G$ and varying $n$ we can
construct what is known as the classifying space for commutativity in $G$. I will survey what is known about these
classifying spaces, whose study is still young.
Links:
[1] http://www.mpim-bonn.mpg.de/de/taxonomy/term/39
[2] http://www.mpim-bonn.mpg.de/de/node/3444
[3] http://www.mpim-bonn.mpg.de/de/TopologySeminar