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Oct 31, 2014 at 12:45 vote accept Haimiao Chen
Oct 31, 2014 at 12:40 vote accept Haimiao Chen
Oct 31, 2014 at 12:45
Oct 31, 2014 at 11:41 answer added Fernando Muro timeline score: 8
Oct 31, 2014 at 11:14 comment added Fernando Muro @AlexSuciu OK, somehow I didn't see "the group ring of".
Oct 31, 2014 at 0:10 comment added Alex Suciu @FernandoMuro: the group ring $\mathbb{Z} G$ of a group $G$ is the free abelian group on $G$ (as a group).
Oct 30, 2014 at 21:08 answer added Allen Hatcher timeline score: 28
Oct 30, 2014 at 16:31 comment added Haimiao Chen @AlexSuciu Thank you. So I know hom complicated the result will be.
Oct 30, 2014 at 16:09 comment added BS. I assume that the group law is addition.
Oct 30, 2014 at 16:07 comment added Fernando Muro @AlexSuciu a non-abelian $\pi_2$?
Oct 30, 2014 at 15:51 comment added Alex Suciu The second homotopy group of $M\# N$ is the group ring of $\pi_1(M)*\pi_1(N)$. Composing with the Hopf map $S^3\to S^2$ yields non-trivial elements of $\pi_3(M\# N)$. When, say, $M$ is a lens space, we also have non-trivial elements of $\pi_3(M\# N)$ coming from $\pi_3(M)=\mathbb{Z}$.
Oct 30, 2014 at 15:30 review First posts
Oct 30, 2014 at 15:47
Oct 30, 2014 at 15:25 history asked Haimiao Chen CC BY-SA 3.0