Espen Nielsen
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 Feb 2 comment $K(G,1)$ for a torsion-free group $G$ @MikeMiller Wall's finiteness obstruction can only be used if you can somehow first show that your complex is finitely dominated, though. Nov 13 revised Smallest 3-category not equivalent to a strict 3-category added 84 characters in body Nov 13 answered Smallest 3-category not equivalent to a strict 3-category Nov 13 comment groupoids and localization in categories Since you are learning homology, the category of chain complexes of abelian groups should be interesting to you. A counter-example to the hypothesis that the localization a category is a groupoid is that there are induced maps on homology which are not isomorphisms. Nov 1 answered If $G$ is a group such that any two commutators commute, $G$ is solvable Oct 28 comment Show $A_n$ has no subgroups of index 2 @Aniket If you read my post, you will see that this is not a question, but a hint for the OP. Oct 28 answered Show $A_n$ has no subgroups of index 2 Oct 28 reviewed Approve Modified Z-transform Oct 27 reviewed Approve outer measure and Sigma algebra of $\mu$-measurable sets Oct 27 reviewed Approve Trig identity $\frac{\cos x}{\sec x} + \frac{\sin x}{\csc x} = \csc^2x - \cot^2x$ Oct 27 reviewed Approve Bracket expansion, keeps failing tests. Oct 26 comment Is it true that $(R\times S)[G]\cong R[G]\times S[G]$? @seeker Do you mean the zero ring? If so, then yes, since $0[G]=0$. Oct 26 comment Is it true that $(R\times S)[G]\cong R[G]\times S[G]$? Did you try to write down some maps between them? Oct 26 comment The rationals as an additive group is free? @Jim This is implicit in the whole discussion. Oct 26 answered The rationals as an additive group is free? Oct 25 reviewed Approve Re-arrangement of a series Oct 24 awarded Yearling Oct 23 reviewed Reject How to find the equation of the graph reflected about a line? Oct 23 reviewed Approve $T^n=1$ then the vector space has $T-$eigenvectors. Oct 23 answered universal property in quotient topology