Timeline for A question on the secondary fan
Current License: CC BY-SA 3.0
4 events
| when toggle format | what | by | license | comment | |
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| Nov 29, 2014 at 22:26 | comment | added | user5117 | No, $X$ itself has Picard number 3; when you contract you get something of smaller Picard number. (This is true even though the contraction is small.) The reason is that any divisor on $X$ that has nonzero intersection number with the contracted curve must push down to a non $\mathbf Q$-Cartier divisor on the image. | |
| Nov 29, 2014 at 22:10 | comment | added | user61586 | Then the picard number of the variety we get in the interior of the face is three. Is this correct? | |
| Nov 29, 2014 at 21:44 | comment | added | user5117 | Proj of a line bundle in the interior of that face is the contraction of the line joining $p_1$ and $p_2$. Proj of a line bundle just on the other side of that face is the flop of that line. | |
| Nov 29, 2014 at 18:36 | history | asked | user61586 | CC BY-SA 3.0 |