Angelo
|
Registered User
|
My name is Angelo Vistoli. I do algebraic geometry, mostly moduli theory.
Normally I don't answer questions from anonymous users. |
|
2h |
comment |
When is the intersection of an isolated normal singularity with a generic linear subspace through that singularity normal? Actually, the way the question was formulated so that the intersection has dimension 2. In this case, to get a positive answer you need the singularity to be Cohen-Macaulay. |
|
7h |
comment |
Finitely-generated abelian group If you can't do your homework problems, I would suggest, first of all, studying, and, if this fails, going to your teacher's office hours. |
|
8h |
comment |
Embedded associated prime and non zero divisor If you can't do your homework problems, I would suggest, first of all, studying, and, if this fails, going to your teacher's office hours. I voted to close. |
|
18h |
accepted | When is the intersection of an isolated normal singularity with a generic linear subspace through that singularity normal? |
|
19h |
answered | When is the intersection of an isolated normal singularity with a generic linear subspace through that singularity normal? |
|
1d |
comment |
Differential form on a compact manifold whose exterior derivative is nowhere zero? Obviously it does not vanish anywhere on $\mathbb R^3$, but you are restricting it to $S^2$, and the restriction map is not pointwise injective. I voted to close as "too localized". |
|
1d |
accepted | Homological characterization of smooth maps |
|
1d |
answered | Homological characterization of smooth maps |
|
May 17 |
revised |
Rigidification and good moduli space (morphism) in the sense of Alper deleted 7 characters in body |
|
May 15 |
accepted | Rigidification and good moduli space (morphism) in the sense of Alper |
|
May 15 |
answered | Rigidification and good moduli space (morphism) in the sense of Alper |
|
May 14 |
comment |
Flatness over Jacboson ring No. Take $A = k[x,y]$, and as $M$ the quotient field of $k[x] = k[x,y]/(y)$. |
|
May 12 |
comment |
Simple automorphism groups of field extensions of infinite transcendence degree I suppose you want $k$ to be also algebraically closed, otherwise the subgroup of elements fixing $\overline k \subseteq K$ would be a proper normal subgroup. I don't have access to Lascar's paper, but from the title I would guess he takes $k = \overline{\mathbb Q}$. |
|
May 12 |
comment |
Proving that a generic variety with ample canonical bundle has no automorphisms I meant this: it is very hard to imagine this might be true, but if it were, it would probably be extremely difficult to prove. In any case, it seems that you are being given counterexamples. |
|
May 12 |
comment |
Proving that a generic variety with ample canonical bundle has no automorphisms You want to do this for every possible family? That is very hard to imagine. |
|
May 9 |
comment |
Etale Cohomology of Punctured Spectra of Local Rings The algebraic cohomology of $\mathbb G_{\rm m}$ is very different from the analytic cohomology of $\mathcal O^*$. For a regular scheme the former is always torsion in degree at least 2 (this is a well-known result of Grothendieck), whereas the analytic cohomology of a complex manifold tends to contain positive-dimensional $\mathbb Q$-vector spaces. |
|
May 7 |
comment |
IGP for non-fixed ground field Please read the FAQ. |
|
May 5 |
comment |
IGP for non-fixed ground field The proof is fine, but the question is off-topic. |
|
May 4 |
comment |
How to show an ideal is Zero-dimensional This sounds like a homework problem. I voted to close. |
|
May 1 |
comment |
Dense Affine Subvarieties of Algebraic Varieties This must be done a little more carefully: the union is not necessarily affine, or even a subvariety. |
|
Apr 30 |
comment |
Uniqueness of deformation family, A first order deformation extends to a miniversal deformation if and only if the corresponding Kodaira-Spencer map is an isomorphism. Your modified deformation obviously satisfies this condition. Then you use uniqueness of miniversal deformations. |
|
Apr 29 |
comment |
Uniqueness of deformation family, What do you mean by an isomorphism of deformations? If the isomorphism is supposed to be over $T$, then the answer is negative, because the two families have different Kodaira-Spencer maps. If, on the other hand, you allow automorphisms of $T$, the answer should be positive for trivial reasons. |
|
Apr 29 |
comment |
Zariski’s main theorem in the form of Grothendieck, universal properties I guess that "Galois with group $G$" should not be interpreted as being necessarily étale. Anyway, it seems to me that (2) and (3) follows immediately from (1), personally I would not worry with a reference. Of course, I am not very good with references. |
|
Apr 27 |
comment |
Tangent space in Algebraic geometry and Differential geometry Can't you work out an example before asking a question? How can you think that the intersection of all curves with a given tangent vector is 1-dimensional? |
|
Apr 26 |
comment |
canonical model of a reducible curve The canonical sheaf of a stable curve with an elliptic tale is not globally generated. |
|
Apr 25 |
accepted | Can Inequivalent Topologies Have Same Sheaves/Cohomology? |
|
Apr 24 |
comment |
Relation of degree and genus of superelliptic curves All this follows easily from Riemann-Hurwitz. |
|
Apr 24 |
answered | Can Inequivalent Topologies Have Same Sheaves/Cohomology? |
|
Apr 20 |
comment |
Kawamata-Viehweg Vanishing Theorem for Excellent Surfaces It follows easily from the fact that a finitely dimensional algebra is Jacobson; in particular, the closed points are dense. So, if there is only one closed point, the spectrum consists of that point, so the algebra is 0-dimensional, hence artinian. |
|
Apr 20 |
comment |
Kawamata-Viehweg Vanishing Theorem for Excellent Surfaces No, a localization is practically never finitely generated. The local rings that are of finite type over a field are artinian. |
|
Apr 20 |
comment |
Kawamata-Viehweg Vanishing Theorem for Excellent Surfaces Since the usual version of the Kawamata-Viehweg vanishing theorem generalized Kodaira's, you'd better write down the exact statement that you need. |
|
Apr 20 |
comment |
pushforward of injective sheaf acyclic for cohomology with supports It seems to the me that the étale case should reduced to the Zariski case, because the pushforward from the étale site to the Zariski site is also flabby. Am I missing something? |
|
Apr 19 |
comment |
Kawamata-Viehweg Vanishing Theorem for Excellent Surfaces Doesn't Kodaira vanishing fail for surfaces in positive characteristic? Raynaud gave counterexamples. |
|
Apr 18 |
comment |
Is there a picture I should have in my head of rational homotopy equivalence? Wasn't it Von Neumann who said that in mathematics you don't understand things, you just get used to them? |
|
Apr 18 |
comment |
Is there an elliptic surface over $Y(1)$? Will Sawin's answer is correct. |
|
Apr 16 |
comment |
What is “Data” involved in a mathematical construction? You would like to be notified in advance? |
|
Apr 15 |
accepted | Semiring of algebraic vector bundles on projective space |
|
Apr 15 |
answered | What is “Data” involved in a mathematical construction? |
|
Apr 14 |
comment |
on flat morphisms Why the heck should it imply that $f$ is flat? Did you forget a hypothesis? |
|
Apr 14 |
comment |
Localization sequence for K^0(X) link.springer.com/chapter/… |
|
Apr 13 |
comment |
A question about fiberbundles in algebraic geometry Locally trivial meaning locally a product? This is an extremely restrictive notion; usually one uses the étale topology. Also, if you want an analogue of the topological notion of fiber bundle even having isomorphic fibers may be too strong. For example, a smooth projective morphism is topologically a fiber bundle, but does not have isomorphic fibers in general. |
|
Apr 10 |
answered | Weil restriction of abelian schemes along finite étale (resp. finite locally free) morphisms |
|
Apr 9 |
accepted | Can one pick generators for the ring of invariants of binary n-ic forms which have rational coefficients? |
|
Apr 9 |
answered | Can one pick generators for the ring of invariants of binary n-ic forms which have rational coefficients? |
|
Apr 7 |
revised |
The sum of same powers of all matrices modulo p deleted 508 characters in body; deleted 7 characters in body |
|
Apr 7 |
answered | The sum of same powers of all matrices modulo p |
|
Apr 6 |
awarded | ● Nice Answer |
|
Apr 6 |
revised |
How to refer to a theorem that you have shown to be wrong deleted 2 characters in body |
|
Apr 5 |
answered | How to refer to a theorem that you have shown to be wrong |
|
Apr 4 |
accepted | Finite-type Artin Stack over $\mathbb C$ |
