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1d
revised (Partial) crepant resolutions
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1d
revised (Partial) crepant resolutions
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comment (Partial) crepant resolutions
ps: if that's your question, then this is an answer, no?
1d
comment (Partial) crepant resolutions
Of course. I was thinking something else. Sorry.
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answered (Partial) crepant resolutions
Jan
11
revised Which curves have reflexive structure sheaf?
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Jan
11
answered Which curves have reflexive structure sheaf?
Jan
2
revised Grothendieck spectral sequence when one of the functors is contravariant
added 3 characters in body
Dec
30
comment necessary conditions for a quadric surface to be ruled (over a field of char 2)
Great answer! Thank you.
Dec
30
comment Grothendieck spectral sequence when one of the functors is contravariant
@MarianoSuárez-Alvarez: I'm not sure what you mean. If this idea works, then there are only finitely many $q$s for which $E_2^{p,q}\neq 0$, so there are only finitely many pages on which there are any non-zero differentials. How could this not converge? (And if it doesn't work, then convergence is not the issue).
Dec
30
revised Grothendieck spectral sequence when one of the functors is contravariant
deleted 1 character in body
Dec
28
awarded  Nice Answer
Dec
27
comment Grothendieck spectral sequence when one of the functors is contravariant
Right, this is a difficulty. However, it is enough to take $\mathscr O(-n)$ for $n\gg 0$ and if $f$ is nice enough (maybe CM?) then you get the vanishing you need. What do you think?
Dec
27
answered Grothendieck spectral sequence when one of the functors is contravariant
Dec
26
comment Is the realtive dualizing sheaf Cohen-Macaulay?
@O-RenIshii: $\omega_X$ exists if $X$ is equidimensional and $\omega_X^\bullet$ (the dualizing complex) exists, i.e., when $X$ is embeddable into a finite dimensional Gorenstein scheme. In particular, it exists if $X$ is finite type over a field. A good definition is this: $\omega_X=h^{-d}(\omega_X^\bullet)$ where $d=\dim X$.
Dec
26
comment Is the realtive dualizing sheaf Cohen-Macaulay?
@MatthieuRomagny: I guess you are right, there is something to be worked out here. I was thinking of using ams.org/journals/tran/2000-352-06/S0002-9947-00-02603-9, but it does not provide a strong CM-ification. I still think this approach should work.
Dec
26
comment Is the realtive dualizing sheaf Cohen-Macaulay?
BTW, the equidimensional assumption is superfluous. If $X$ is CM, then each connected component is equidimensional.
Dec
25
answered Is the realtive dualizing sheaf Cohen-Macaulay?
Dec
18
comment Elliptic fibration arising from a higher genus linear system
I don't see how a general element of a pencil can have more than one component which is not part of the fixed part. Do you have an example when $r>1$?
Dec
18
answered Maximal ideals of polynomial ring containing a fixed element