Timeline for Discriminants of indefinite integral binary quadratic forms admitting 3 or 6 torsion.
Current License: CC BY-SA 3.0
8 events
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| Apr 13, 2017 at 12:19 | history | edited | CommunityBot |
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| Jul 27, 2016 at 17:16 | history | edited | Will Jagy | CC BY-SA 3.0 |
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| Jul 27, 2016 at 16:50 | comment | added | Stanley Yao Xiao | Yes, that is true and can be proved | |
| Jul 27, 2016 at 16:46 | history | edited | Will Jagy | CC BY-SA 3.0 |
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| Jul 27, 2016 at 16:33 | comment | added | Will Jagy | @StanleyYaoXiao thanks. I use the intersection with $SL_2 \mathbb Z,$ that is determinant $1$ and infinite cyclic, just parametrized by Pell. Is that still true without reservations? Second note, i have posted many Conway topograph diagrams on MSE, maybe I can just put a bunch of links into this answer... | |
| Jul 27, 2016 at 14:43 | comment | added | Stanley Yao Xiao | There are mistakes in Bachmann and Vollmer's book. For example, the automorphism group $\operatorname{Aut}(f)$ is not just $\langle -1 \rangle \times \langle T \rangle$ as claimed... there are potentially infinitely many $2$-torsion elements. For example, consider $x^2 - 2y^2$. The matrix $\begin{pmatrix} 3 & 4 \\ -2 & -3 \end{pmatrix}$ is a non-trivial $2$-torsion automorphism. | |
| Jun 12, 2013 at 1:38 | history | edited | Will Jagy | CC BY-SA 3.0 |
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| Jun 12, 2013 at 1:29 | history | answered | Will Jagy | CC BY-SA 3.0 |