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Jul 27, 2010 at 15:12 history edited Francesco Polizzi CC BY-SA 2.5
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Jul 27, 2010 at 14:47 comment added Francesco Polizzi Ad actually they were different... The behaviour of the sheaves $\mathcal{O}_X(n)$ in the weighted projective spaces is not the same as in the usual projective space, as you pointed out, so I had to be more accurate and take the double dual into account. I've edited the answer, anyway. Thank you for the remark.
Jul 27, 2010 at 14:46 history edited Francesco Polizzi CC BY-SA 2.5
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Jul 27, 2010 at 14:42 comment added Donu Arapura Right. I think that $ (\mathcal{O}_X(1) \otimes \mathcal{O}_X(1))^{**}\cong \mathcal{O}_X(2)$ should be fine, but it wouldn't be true without the double dual.
Jul 27, 2010 at 14:36 history edited Francesco Polizzi CC BY-SA 2.5
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Jul 27, 2010 at 14:02 comment added Francesco Polizzi I understand your doubt. Are you suggesting that $\mathcal{O}_X(1) \otimes \mathcal{O}_X(1)$ could be actually different from $\mathcal{O}_X(2)$, aren't you? Looking at the definitions, I know that these two sheaves agree in a dense open subset of $X$, but this is actually not enough to conclude. I will check it out...
Jul 27, 2010 at 13:36 comment added Donu Arapura I have to apologize for the way this sounds, but this seems suspect. Are you sure there isn't a double dual in there somewhere?
Jul 27, 2010 at 13:30 history edited Francesco Polizzi CC BY-SA 2.5
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Jul 27, 2010 at 13:23 history answered Francesco Polizzi CC BY-SA 2.5