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Jan 2, 2019 at 23:47 answer added thierry stulemeijer timeline score: 5
Nov 11, 2018 at 15:39 vote accept D_S
Nov 11, 2018 at 7:18 answer added Venkataramana timeline score: 7
Nov 11, 2018 at 1:57 comment added YCor OK: these are precisely the nondiscrete locally compact fields.
Nov 10, 2018 at 23:48 comment added D_S I just mean $\mathbb R, \mathbb C$, or a finite extension of $\mathbb Q_p$ or $\mathbf F_q((t))$
Nov 10, 2018 at 22:33 comment added YCor Borel-Serre (CMH 1964) obtains the finiteness of the relevant cohomology groups when one has a perfect field with finitely many extensions of each degree. This probably yields the openness result in this case. The openness result fails for the non-perfect locally compact field $K=\mathbf{F}_p((t))$ and $G\to G/H$ for $G=\mathrm{SL}_p$, $H=\mathrm{PGL}_p$.
Nov 10, 2018 at 22:29 comment added YCor Would you specify what you call a local field? Everybody agrees that $\mathbf{Q}_p$ is a local field, but some define it as an arbitrary nondiscrete locally compact field (which is a reasonable setting for your question), while others would exclude $\mathbf{R}$ but would allow some non-locally compact fields such as Laurent Series over infinite discrete fields.
Nov 10, 2018 at 21:24 history asked D_S CC BY-SA 4.0