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Sep
21
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Aug
31
comment Prerequisites and references for homological algebra
@MathematicalPhysicist: Nearly all the typographical errors (that I could find, of course, and many that I couldn't) of Weibel's text have been listed on his website for some time.
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....