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seen Dec 13 at 10:14

Aug
25
accepted Homology of a finite graph follows from Mayer-Vietoris sequence?
Aug
24
comment Homology of a finite graph follows from Mayer-Vietoris sequence?
@LeeMosher Thanks. I've edited to include these.
Aug
24
revised Homology of a finite graph follows from Mayer-Vietoris sequence?
added 104 characters in body
Aug
24
asked Homology of a finite graph follows from Mayer-Vietoris sequence?
Aug
24
revised A generalization of Jordan curve theorem to connected open sets in the plane
edited body
Aug
22
reviewed Approve Equality of subgroups $H \subseteq K \subseteq G$ with the same finite index in $G$
Aug
22
asked Cycles non-homologous but with the same winding number at each point outside?
Aug
21
accepted A generalization of Jordan curve theorem to connected open sets in the plane
Aug
21
accepted Cover a sphere by two closed subsets not containing a closed self-antipodal connected subset?
Aug
20
asked A generalization of Jordan curve theorem to connected open sets in the plane
Aug
20
comment Cover a sphere by two closed subsets not containing a closed self-antipodal connected subset?
@Timkinsella Good. Make it an answer and I'll accept it. Thanks!
Aug
20
asked Cover a sphere by two closed subsets not containing a closed self-antipodal connected subset?
Jul
30
revised Generalizing a statement about direct limits in the category of $A$-modules to other categories
added 10 characters in body
Jul
30
asked Generalizing a statement about direct limits in the category of $A$-modules to other categories
Jul
24
comment Surjectivity implies injectivity of finitely generated modules, localization?
@user26857 Right, but I only asked for a geometric meaning, not claimed that there should be. I asked since I feel that I don't really understand the determinant trick and it's still a very tricky stuff to me. I don't understand the underlying reason why viewing $M$ as an $A[X]$-module is that efficient, say, to obtain Frobenius normal forms for matrices, or in proof of Nakayama's lemma.
Jul
23
revised Surjectivity implies injectivity of finitely generated modules, localization?
added 477 characters in body
Jul
23
comment Surjectivity implies injectivity of finitely generated modules, localization?
@MartinBrandenburg Yeah, it might be frustrating. Incidentally, is there any geometric viewpoint of viewing $M$ as an $A[X]$ module by action $X.m=f(m)$?
Jul
23
comment Surjectivity implies injectivity of finitely generated modules, localization?
@MartinBrandenburg I didn't understand your point, but by Nakayama, the surjectivity of $M\otimes_k k\xrightarrow{f\otimes1}M\otimes_k k$ implies the surjectivity of $M\xrightarrow fM$. See, for example, Atiyah & Macdonald, Ex 2.10.
Jul
22
revised Surjectivity implies injectivity of finitely generated modules, localization?
added 220 characters in body
Jul
22
revised Equation for the length of a chord parallel to either the minor or major axis in an ellipse
edited tags