most recent 30 from http://mathoverflow.net 2013-06-20T10:33:07Z http://mathoverflow.net/feeds/user/1852 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/4578/subgroups-of-free-abelian-groups-are-free-a-topological-proof/5771#5771 Andrew S 2009-11-17T03:39:00Z 2009-11-17T03:39:00Z

<p>For a purely topological proof of the statement "Every subgroup of a free abelian group is free abelian.", why not just continue to use a wedge of circles, but use the first simplicial homology and the Hurewicz theorem? If you take "free abelian" to mean "a direct limit of finte rank free abelian", it seems to follow from the statement about free groups.</p>