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Feb
4
revised A form of Künneth formula?
added 69 characters in body
Feb
4
asked A form of Künneth formula?
Jan
28
awarded  Yearling
Jan
28
comment When are two direct products of groups isomorphic?
For finitely generated Abelian groups, it seems right, as a result of the structure theorem. In general, maybe Jordan-Hölder theorem works. I don't know.
Jan
28
accepted Homotopically equivalent to Čech nerve?
Jan
28
revised A maximal inequality on distance to median, so called Lévy's inequality?
added 241 characters in body
Jan
28
comment When are two direct products of groups isomorphic?
In infinite case, $H_1\cong H_2$ isn't necessary. Note that $\mathbb Z^\omega\times\mathbb Z^\omega\cong\mathbb Z^\omega$. That's simply to say, $\omega+\omega=\omega$, where $\omega$ is the countable cardinal.
Jan
28
comment Homotopically equivalent to Čech nerve?
@anomaly Well, I need time to read it. Please post an answer here so that I can accept it. That's exactly what I want.
Jan
28
comment When are two direct products of groups isomorphic?
Are you only interested in the finite case?
Jan
28
comment Homotopically equivalent to Čech nerve?
@anomaly I skimmed the proof and maybe the paracompactness is only used to give a partition of unity? It seems to me that the local finiteness of $\mathfrak U$ gives a partition of unity. I haven't gone through homotopy theory. I only want a reference to see what's the idea involved. Thanks!
Jan
28
revised Homotopically equivalent to Čech nerve?
added 64 characters in body
Jan
28
asked Homotopically equivalent to Čech nerve?
Jan
28
accepted A seemingly wrong definition of convergence of spectral sequences in Bott & Tu?
Jan
25
asked A seemingly wrong definition of convergence of spectral sequences in Bott & Tu?
Jan
21
revised Exercise from Geometry of algebraic curves by Arbarello, Cornalba, Griffiths, Harris
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Jan
21
revised Exercise from Geometry of algebraic curves by Arbarello, Cornalba, Griffiths, Harris
Add tags.
Jan
19
comment Conditions on ideal b for fields or integral domains
It might be worthy to explicate the reason for me (and maybe others) to vote to close the question, and it might be the probable reason for these downvotes. That is to say, you have to write down your efforts when you post questions. It's a convention and a formal etiquette. It may not be that reasonable, though.
Jan
19
revised Conditions on ideal b for fields or integral domains
Retag
Jan
19
revised How to remember all the proofs in mathematics
added 2 characters in body
Jan
19
comment If $f$ is a continuous function in $[a,b]$ whose derivative $f~'$ exists at every point $c \in [a,b]$. Then, is $f~'$continuous?
Related: math.stackexchange.com/q/112067/23875