Skip to main content
7 events
when toggle format what by license comment
Jun 28, 2023 at 14:16 history edited YCor CC BY-SA 4.0
fixed typo, added tag
Aug 6, 2014 at 14:23 comment added Keivan Karai user52824: Thank you for the enlightening comment. I soon have to deal with several other cases (including different ${\mathbf Q}_p$-forms of ${\mathrm{SO}}_4$.) It would be great if you could please provide a reference that explains how to systematically find all these forms.
Aug 5, 2014 at 15:10 comment added user27920 Forms of ${\rm{SO}}_3$ are the same as forms of ${\rm{PGL}}_2$, and those in turn correspond to isomorphism classes of quaternion algebras. By our knowledge of the Brauer group of local fields, there are exactly two such algebras over any local field. The corresponding groups are split (for the matrix algebra) and anisotropic (for the division algebra).
Aug 5, 2014 at 14:04 vote accept Keivan Karai
Aug 5, 2014 at 13:46 answer added abx timeline score: 7
Aug 5, 2014 at 13:44 comment added YCor No, since the dimension is odd, up to scaling you can suppose the determinant equal to $-1$, so the only remaining invariant is $\epsilon\in\{\pm 1\}$, and then for $\epsilon=1$ the form is isotropic (hence the group non-compact) and for $\epsilon=-1$ its anisotropic (and hence the group compact).
Aug 5, 2014 at 13:27 history asked Keivan Karai CC BY-SA 3.0