Reputation
1,431
Next privilege 2,000 Rep.
Edit questions and answers
Badges
10 16
Newest
 Enlightened
Impact
~89k people reached

Dec
7
awarded  Enlightened
Dec
7
awarded  Nice Answer
Nov
20
comment Good reduction and blow-ups
@Laurent : Is it really needed that T is a relative local complete intersection? It seems to me that flatness of T and X already give flatness of all powers $I^n$ and quotients $I^n / I^{n+1}$, and so the commuting with base change. Is that not so? Thanks!
Nov
19
awarded  Yearling
Nov
19
awarded  Yearling
Sep
30
awarded  Explainer
Jul
2
awarded  Curious
Mar
11
comment Automorphisms of a smooth quadric surface $Q\subset\mathbb{P}^{3}$
Any automorphism must preserve the intersection product, so it either preserves or exchanges the two rulings. Using this you should be able to prove what you want.
Mar
11
awarded  Citizen Patrol
Feb
27
awarded  Nice Question
Feb
5
comment Who stated and proved the “Hopf lemma” on bilinear maps?
@QiaochuYuan: added clarification in the body of the question.
Feb
5
revised Who stated and proved the “Hopf lemma” on bilinear maps?
clarification in reply to a comment
Feb
4
comment Who stated and proved the “Hopf lemma” on bilinear maps?
This is really relevant, and seems to support the idea that, after Hopf's work, the result became known (even for an arbitrary algebraically closed field, not C!) But Saint-Donat does not even mention Hopf or anybody else...
Feb
4
asked Who stated and proved the “Hopf lemma” on bilinear maps?
Feb
4
comment Symmetric product of global sections on a curve
@aginensky I see, thanks.
Feb
3
comment Symmetric product of global sections on a curve
Is it easy to see that $\dim W\ge 2\dim V-1$? Is it in Arbarello-Cornalba-Griffiths-Harris? Or on some other reference? Thanks.
Feb
3
comment Why aren't fields called “bodies” instead?
In European Spanish it is "cuerpo" indeed, but it is "campo" in Mexican Spanish, clearly by US influence. I don't know how far south in America this goes, nor whether they use "cuerpo" for skew fields. By the way, I believe that in Spain skew fields are generally called "anillos de división" (division rings) but "cuerpos no conmutativos" is not unheard of.
Dec
22
comment Is Euclid dead?
Also, it seems perfectly possible that critical thought existed, but that for a sufficiently large mass of young people the bullshit had stronger impact than the proofs. I simply don't know.
Dec
22
comment Is Euclid dead?
@SergeiAkbarov, I think Latin fell out of the western curricula more or less at the same time as Euclidean Geometry. Some little Philosophy and Logic do remain (at least in some countries). Anyway, how much faith can one retain that teaching proofs, in itself, will be determinant for building critical thought? Isn't the USSR system that you explain a counterexample?
Nov
20
comment Deformation of a family of curves in a surface
Do you mean, for each divisor in U there is a deformation of S which contains it?