Timeline for Index of subgroups of $\mathrm{Sp}(4,\mathbb{Z})$ conjugate in $\mathrm{GL}(4,\mathbb{Q})$
Current License: CC BY-SA 4.0
6 events
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| Jan 12, 2022 at 16:41 | comment | added | LSpice | @YCor, that seems to be an answer (I wouldn't have guessed that such high-powered techniques were required, but certainly no more elementary argument occurs to me); would you post it as such? | |
| Jan 12, 2022 at 16:06 | history | edited | T.Ch. | CC BY-SA 4.0 |
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| Jan 9, 2022 at 21:43 | comment | added | YCor | Yes. If both indices are both finite, this is a consequence of Harish-Chandra (which ensures these are lattices) and Mostow's theorem (which implies they are conjugate in the real group, so have the same covolume). To exclude the case one index is finite and the other is infinite, one can invoke Margulis' superrigidity. | |
| Jan 9, 2022 at 21:41 | history | edited | YCor | CC BY-SA 4.0 |
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| S Jan 9, 2022 at 19:41 | review | First questions | |||
| Jan 9, 2022 at 20:03 | |||||
| S Jan 9, 2022 at 19:41 | history | asked | T.Ch. | CC BY-SA 4.0 |