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Sep 18, 2013 at 8:23 comment added HJRW Here's another necessary condition: if your group $G$ is not free, then $b_2(G)>0$. Stallings proved (Homology and central series of groups, J. Algebra) that, in a group with $H_2(G,\mathbb{Q})=0$, any linearly independent subset in $H_1$ generates a free subgroup. But the generating set in your presentation is linearly independent in $H_1$.
Sep 17, 2013 at 17:00 history edited Nick Salter CC BY-SA 3.0
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Sep 17, 2013 at 16:58 comment added Nick Salter Yes, I mean a product of commutators. I'll edit the language to make it more precise.
Sep 17, 2013 at 15:49 comment added HJRW To be clear, for you, a 'commutator relation' is a relation which is a product of commutators, right?
Sep 17, 2013 at 15:31 comment added Nick Salter Ah - that's a good point. I've edited my question.
Sep 17, 2013 at 15:30 history edited Nick Salter CC BY-SA 3.0
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Sep 17, 2013 at 15:23 comment added Andy Putman This is impossible. The trivial group is the only group with this property whose abelianization is trivial, so if you could solve this problem then you could decide whether a group presentation gave the trivial group.
Sep 17, 2013 at 15:18 history asked Nick Salter CC BY-SA 3.0