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Jul
6
comment Free modules are projective.
@peterag: Thanks very much! A terrible omission on my part :)
Jul
6
revised Free modules are projective.
forgot a word
Jun
29
comment $M_1$, $M_2$ and $M_1\cap M_2$ injective imply $M_1+M_2$ is also injective?
@PtF: Sounds good
Jun
29
comment What is $\operatorname{Hom}_R(P,R)$ isomorphic to when $P$ is projective?
@user26857: The answer to your question is false, e.g. $\mathrm{Hom}(\oplus^\omega \mathbb{Z},\mathbb{Z})\cong\prod^\omega\mathbb{Z}$.
Jun
29
revised $M_1$, $M_2$ and $M_1\cap M_2$ injective imply $M_1+M_2$ is also injective?
typo fix
Jun
29
answered $M_1$, $M_2$ and $M_1\cap M_2$ injective imply $M_1+M_2$ is also injective?
Jun
28
comment Ext$_R^n(Q,A)=0=$Tor$_n^R(Q,A)$ where $Q$ is the field of fractions of a domain $R$
@1234: Yes, that sounds good! However, for the isomorphism part, you can still use the fact that any map $Q\to Q$ extends uniquely up to chain homotopy to the projective resolution.
Jun
27
answered Ext$_R^n(Q,A)=0=$Tor$_n^R(Q,A)$ where $Q$ is the field of fractions of a domain $R$
Jun
14
answered functor of points for grassmannian
Jun
14
answered Is this a typo in Weibel, page 1?
Jun
14
comment In a reduced ring the set of zero divisors equals the union of minimal prime ideals.
@EricTowers: Thanks, corrected.
Jun
14
revised In a reduced ring the set of zero divisors equals the union of minimal prime ideals.
edited body
Jun
13
comment In a reduced ring the set of zero divisors equals the union of minimal prime ideals.
@user26857 - Didn't notice that, thanks! However, I still feel it's more convenient to have a self-contained solution with notation in line with the entire answer rather than jump to another page with a different notation.
Jun
13
answered In a reduced ring the set of zero divisors equals the union of minimal prime ideals.
May
6
answered Group theory and Complex Analysis
May
4
comment Heuristic: Daniell integral vs. Lebesgue integral
A similar question you might find useful: math.stackexchange.com/questions/175991/…
Apr
27
comment Vector Bundles:differential geometry vs algebraic geometry
I believe a superior source to Hartshorne is Gortz and Wedhorn's "Algebraic Geometry I", chapter 11.
Apr
3
comment Examples of real world situations where mathemematical rigour is needed
A level of rigour is definitely required for applying statistical results to the real world. You could get an idea of this at the cross validated site....
Mar
27
answered Why are cohomotopy groups defined only up to dimension $2m-2$ and not $2m-1$?
Mar
20
comment Multiple categorifications of structures
@QiaochuYuan: Yes. That is true, it is too narrow to include the finite sets example. However, I wasn't aiming at a good general definition of categorification, only to provide some examples for some definition of categorification.