Timeline for Some Elementary Schubert Calculus Calculations
Current License: CC BY-SA 3.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 30, 2018 at 15:04 | comment | added | Rene Schipperus | Yes that is exactly what it is, the tangency of the double point counts twice. I tried to omit that idea for the posting, foolish. These are "complete conics" consisting of the point curve together with all tangents. The degenerate double point conic consists of two line with all lines through the point of intersection as tangent lines, and counted with multiplicity $2$. | |
| Mar 30, 2018 at 14:59 | comment | added | aglearner | 34 could be just $17\cdot 2$ which would mean that we consider ordered pairs of lines? I guess $33$ stands for reducible conics - here there is no ordering... | |
| Mar 30, 2018 at 14:52 | comment | added | Rene Schipperus | Yes, but $34$ is the correct answer. I think he has missed a multiplicity somewhere or I explained the problem poorly. | |
| Mar 30, 2018 at 14:17 | comment | added | aglearner | Yes, you are right - this is the line that intersects all four $l_i$, and as Jason says, such a double line has multiplicity $8$ (though I can not make this calculation) - leading to his $33$. | |
| Mar 30, 2018 at 14:03 | comment | added | Rene Schipperus | Thanks, for the answer !, Through $l\cap P$ there are also two lines but they are concurrent with $l$ and not coplanar, which is why they must be subtracted. | |
| Mar 30, 2018 at 13:57 | history | answered | aglearner | CC BY-SA 3.0 |