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Apr
28
comment local description of $\mathbb{P}^2$-fibrations over $\mathbb{P}^1$
@Sasha Nice reference, but only the case where the degenerating surface has quotient singularity is treated. Is there a way in general to have some kind of "canonical" birational map to a P^2 bundle? Or at least to something with mild singularities? (when I mean canonical, I mean something that would be equivariant why any group action).
Apr
23
answered Irreducible variety
Feb
28
answered Étale coverings of cubics and gluings
Feb
28
comment Étale coverings of cubics and gluings
Yes but the exchanges is not compatible with the morphism $\tilde{X}\to X$.
Feb
12
answered One-dimension Algebraic groups
Feb
3
awarded  Popular Question
Dec
19
accepted Rational solutions of the Fermat equation $X^n+Y^n+Z^n=1$
Dec
15
awarded  Nice Question
Dec
14
revised Rational solutions of the Fermat equation $X^n+Y^n+Z^n=1$
deleted 172 characters in body
Dec
14
asked Rational solutions of the Fermat equation $X^n+Y^n+Z^n=1$
Dec
6
comment Pushing-forward morphisms
Nice answer. Thank you.
Dec
6
accepted Pushing-forward morphisms
Dec
4
awarded  Nice Question
Dec
4
awarded  Inquisitive
Dec
3
comment Pushing-forward morphisms
Thanks Jason, this is a nice answer +1! It seems that you did not even use anything like non-ramified, right? Unfortunately, I would like such kind of result where $Y$ is not normal (neither is $X$ or $Z$) and also I would also be happy to have something in characteristic $p$ (but maybe it is too much to ask). I would be happy with $f$ and $\psi$ proper (to avoid the counterexamples you gave), and I added the condition of being unramified to remove the case of a morphism $X\to Z$ from a smooth curve to a cusp (for example). But maybe it does not work?
Dec
3
asked Pushing-forward morphisms
Nov
21
comment Existence of a continuous section
Thanks for the nice comment. I did not know about this result. Are there some examples where $Y=[0,1]$ ?
Nov
21
asked Existence of a continuous section
Nov
16
reviewed Approve Is there a name for this fast growing functions?
Nov
16
reviewed Approve Is a Laskerian ring coherent