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Jan
7
comment When can a locally compact group be approximated by discrete subgroups?
I don't know if this helps for the application you have in mind, but for t.d.l.c. groups, an alternative way to approximate the group by discrete objects is to look instead at coset spaces $G/U$ where $U$ ranges over a base of identity neighbourhoods consisting of compact open subgroups. If $G$ is a SIN group, then you can also make $U$ normal in $G$, so $G/U$ is a discrete quotient group of $G$ in the natural sense.
Jan
1
reviewed Approve The injection of direct image sheaf
Dec
10
reviewed Approve Projective closure of affine curve
Dec
10
reviewed Approve Number of spanning trees which contain a given edge
Dec
10
revised Distal actions on coset spaces
added 439 characters in body
Dec
10
revised Can Calabi-Yau manifolds have nonabelian discrete symmetry groups?
edited tags
Dec
7
revised Distal actions on coset spaces
added 175 characters in body
Dec
7
asked Distal actions on coset spaces
Dec
6
reviewed Approve Completion of modules of differentials (A strange exercise in Liu's AG textbook)
Dec
5
reviewed Approve Mystery behind ADE Dynkin diagram
Dec
3
answered Wild automorphisms of profinite groups
Nov
10
comment What are some very important papers published in non-top journals?
@GerryMyerson: Indeed, thanks!
Nov
8
comment What are some very important papers published in non-top journals?
I think there was a similar question (which I can't find right now) about important original theorems appearing in books rather than journals. The Dicks-Dunwoody almost stability theorem comes to mind (although it is slightly before the cutoff date).
Oct
27
comment A generalization of residual finiteness to topological groups
A discrete cocompact normal subgroup $\Lambda$ is already a lot to ask for. For instance, if your group is compactly generated, then any such $\Lambda$ must have open centraliser, so if $G$ is connected then $\Lambda$ would be central, and if $G$ is totally disconnected you'd have a finite index subgroup of the form $\Lambda \times U$ where $U$ is a compact open subgroup.
Oct
22
revised Not especially famous, long-open problems which anyone can understand
added 207 characters in body
Oct
22
answered Not especially famous, long-open problems which anyone can understand
Sep
23
revised Just-not-nilpotent-by-compact quotient of a locally compact group
added 73 characters in body
Sep
23
answered Just-not-nilpotent-by-compact quotient of a locally compact group
Sep
16
comment Actions on spaces with measured walls
Groups acting on $\mathbb{R}$-trees could be a good special case to consider.
Sep
14
awarded  Civic Duty