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seen Jan 29 at 7:56

Jan
28
answered Universal Cover of the Punctured Torus
Jan
28
comment The prime ideals of the ring $K[x]$
@Andrew: sorry, I misread your question and I deleted my comment. Also: think about Krish's very judicious comment.
Jan
28
answered Why do we require that a complex manifold has the structure of a real manifold?
Jan
27
comment Checking normality for quasi compact schemes
Ah, that explains it: his fantastic notes are extremely original and contain a wealth of results not to be found elsewhere.
Jan
27
comment Checking normality for quasi compact schemes
Ah, thank you for your quick answer. I asked because the result in your exercise doesn't seem to be mentioned in the standard books. Your exercises are rather sophisticated, apparently!
Jan
27
comment Checking normality for quasi compact schemes
Dear user, how do you know that each point is a generization of some closed point?
Jan
27
answered Checking normality for quasi compact schemes
Jan
27
comment Show that $X$ is not an affine variety
Un' ottima risposta, caro Sergio !
Jan
27
comment Flatness of integral closure over an integral domain
Dear user 2219896: +1 for your question too, and all my wishes for your future personal situation.
Jan
27
comment Flatness of integral closure over an integral domain
Dear @user2219896: +1 (on the linked post) for your explanation/calculation and your kind offer to the OP. I personally knew the solution to step 2 (it's even at the back of the book!) but I didn't post it because , even if I argued with you in my first comment, I considered the decision was yours.
Jan
26
comment Flatness of integral closure over an integral domain
Dear @user26857, yes I understand your point of view, even if I have to confess that I didn't find the second step easy at all. Anyway, and more importantly, I'll take this opportunity to tell you how much I enjoy your posts which always very insightfully go straight to the heart of the matter. I'm looking forward to your next ones!
Jan
26
comment Flatness of integral closure over an integral domain
@user26857: your answer in the link indeed shows elegantly how to prove the general result. The OP however knows that the result holds without any finiteness asumption. In order to make the case that such an assumption does not really simplify the proof, you might want to add a few more hints/references in your answer, in particular since it refers to an exercise in Matsumura. Even if the OP doesn't need such complements, other users might welcome them. That said, you are the only master on board of your answer ...
Jan
26
comment (un)Intentionally funny titles of mathematical works
Dear Arturo, users on this site and MathOverflow have various qualities, but a sense of humour is, alas, not the most widespread one. I deplore it.
Jan
26
comment Using Comma in if…then Conditional Sentences
@Clarinetist: mathematicians are English grammar experts. More precisely, mathematicians are the most knowledgeable about foreign languages among any group of people having university degrees, including professional linguists. I'm not sure about clarinetists, however...
Jan
26
revised Universal Cover of $\mathbb{R}P^{2}$ minus a point
added 153 characters in body
Jan
26
answered Universal Cover of $\mathbb{R}P^{2}$ minus a point
Jan
25
comment Presheaf image of a monomorphism of sheaves is a sheaf
This answer is indeed perfectly correct, contra mez's assertion.
Jan
24
comment Stokes or homotopy?
You are welcome, dear Alonso.
Jan
24
comment Finding two inequivalent closed, non-exact $1$-forms on $T = S^1 \times S^1$: second check
Your notation is not clear: as far as I understand $\theta_U=\varphi_U$, so that the use of two different letters is unnecessary. What are for example $\theta_U(1,0)$ and $\varphi_U (1,0)$ (Supposing that $S^1$ is given by $x^2+y^2=1$ ) ? If you don't believe these charts are equal, at what point would they have different values?
Jan
24
comment When is the symmetric algebra of a vector bundle finitely-generated?
Very interesting answer!