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15 votes
1 answer
784 views

The completion of the space of finite groups

Edit: I revise the question based on the comment conversations Let $\mathcal{F}$ be the set of all equivalence classes of finite groups under the "Isomorphism" equivalence relation. We define ...
Ali Taghavi's user avatar
5 votes
2 answers
349 views

Codimension-1 subgroups of 3-manifold groups

Let $G$ be a finitely generated group and let $H$ be a subgroup of $G$. $H$ is a codimension-1 subgroup of $G$ if $C_{G}/H$ has more than one end, where $C_{G}$ is the Cayley graph of $G$. Do all ...
Gus's user avatar
  • 85
5 votes
1 answer
287 views

Extreme amenability of topological groups and invariant means

Recently I'm reading the paper Ramsey–Milman phenomenon, Urysohn metric spaces, and extremely amenable groups by Pestov. When it comes to the definition of an extremely amenable topological group, it ...
Muduri's user avatar
  • 225
4 votes
0 answers
72 views

When is the submonoid preserving a subspace finitely generated?

Let $T$ be a topological space with at least one open set whose closure is not open. Let $G$ be a finitely generated group acting by homeomorphisms on $T$. Let $S\subset T$ be a subspace. Under what ...
Nassim's user avatar
  • 51
3 votes
1 answer
267 views

In what sense is every element of $H_2(G)$ "represented by a free action on some surface"

(This is a cross-post of this unanswered math.stackexchange question) In Edmond's 1982 paper Surface Symmetry II, at the bottom of page 145, he writes: "Corollary - If $G$ is a split nonabelian ...
stupid_question_bot's user avatar
1 vote
1 answer
313 views

Group action on quasi-isometric geodesic metric space [closed]

If a group $G$ acts on a geodesic metric space $X$, then does $G$ act on a geodesic metric space $Y$ which is quasi-isometric to $X$?
Anton's user avatar
  • 81