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visits member for 1 year, 8 months
seen Aug 17 at 16:52

Jul
2
awarded  Curious
Dec
23
comment To what extent does the branch locus determine the covering (Chisini's conjecture)?
And yes, I'm interested in positive results, and I am not sure the suggested construction will yield counterexamples.
Dec
23
comment To what extent does the branch locus determine the covering (Chisini's conjecture)?
@Jason: if the surface $X$ is irreducuble, then the homomorphism $\pi_1(\mathbb P^2\setminus S,p)\to \mathrm{Aut}(f^{-1}(p))$ is automatically surjective.
Dec
23
asked To what extent does the branch locus determine the covering (Chisini's conjecture)?
Dec
16
awarded  Yearling
Nov
25
comment Is the Picard number bounded by $b_2$ in positive characteristic?
A minor correction: in char 0, $\rho(X)\le b_2(X)$, not necessarily strictly less.
Nov
24
revised arctan of a square root as a rational multiple of pi
corrected tags
Nov
24
suggested suggested edit on arctan of a square root as a rational multiple of pi
Nov
23
comment rational map becomes a morphism after blow-ups
@Jason: that's right, of course, but I believe the OP meant blow-ups with smooth centers (and rational map of smooth varieties).
Nov
23
awarded  Informed
Nov
16
accepted Self-dual surfaces in $\mathbb P^3$ with isolated singularities
Nov
16
comment Self-dual surfaces in $\mathbb P^3$ with isolated singularities
@Francesco: thank you
Nov
16
revised Self-dual surfaces in $\mathbb P^3$ with isolated singularities
a TeX error
Nov
16
asked Self-dual surfaces in $\mathbb P^3$ with isolated singularities
Sep
6
comment On Serre's twisting sheaf
If $Y$ is a cone, then all these maps are surjective. If the Zariski tangent space at at least one point of $Y$ has dimension $n$, then $H^0(\mathcal O_{\mathbb P^n}(1))$ surjects on $H^0(\mathcal O_Y(1))$ (I am not sure about $\mathcal O(j)$ with $j>1$). I would not say these results are general enough.
Sep
5
answered References on complete intersections in Grassmanian
Aug
18
comment General curves of genus 3 as plane sections of Kummer surfaces
Sorry, do you really mean «generically injective»? If a quartic has automorphisms, then the mapping in question from $(\mathbb P^3)^*$ to $M_3$ cannot be generically injective. Did you actually mean «has 3-dimensional image»?
Aug
18
comment General curves of genus 3 as plane sections of Kummer surfaces
Thank you, interesting indeed. Is this problem open even for the case of smooth quartics?
Aug
17
comment General curves of genus 3 as plane sections of Kummer surfaces
Many many thanks!
Aug
17
accepted General curves of genus 3 as plane sections of Kummer surfaces