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Hi,

this question concerns the canonical bundle $\omega_X$ on a smooth projective $k-$variety $X$.

I want to consider the diagonal embedding

$i:X\rightarrow X\times X$

on $X$.

Furthermore denote by $p$ the projection $X\times X \rightarrow X$ on the first factor.

Now my question:

does it hold that

$i_*\omega_X \simeq p^* \omega_X$

canonically as sheaves on $X\times X$?

I thank you very much!

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    $\begingroup$ Well, $p^* \omega_X$ is locally free (and nonzero) so its support is all of $X\times X$, and on the other hand the support of $i_* \omega_X$ is contained in the diagonal $\Delta \subseteq X\times X$. $\endgroup$
    – Mattia Talpo
    Commented Aug 21, 2011 at 8:38
  • $\begingroup$ So, it is false. Thank you, Mattia! $\endgroup$
    – ernest
    Commented Aug 21, 2011 at 10:00

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