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Questions about the branch of algebra that deals with groups.

4 votes
2 answers
467 views

$H_2(H,\mathbb{Z})$ where $H$ is a f.g. normal subgroup of a f.p. group

Let $G$ be a finitely presented group and $H$ a finitely generated normal subgroup. Is it always true that the Schur Multiplier $H_2(H,\mathbb{Z})$ is a direct product of finitely generated abelian gr …
4 votes
1 answer
507 views

Quotients of the Higman Group

Chou asked in this paper whether The Higman group $H$ has a maximal normal subgroup $N$ such that $H/N$ has no (non-abelian) free subgroups (or is amenable). Is it known now if such subgroups exist …
5 votes
1 answer
228 views

Amenable groups with special presentations

Is there a group with a presentation $\left< X \mid r_i, i \in \mathbb{N} \right>$ (where $X$ is finite) with $\left< X \mid r_i, i \in A \right>$ is amenable if and only if $A\subset \mathbb{N}$ …
12 votes
2 answers
816 views

Finitely generated subgroups with infinite cyclic quotient

Suppose that $G$ is a finitely presented group and $H$ is a finitely generated normal subgroup such that $G/H$ is infinite cyclic. Is it true that $H$ is finitely presented?
7 votes
0 answers
177 views

Countable elementary sub-structure of the automorphism group of the binary rooted tree

Let $G$ be the automorphism group of the binary rooted tree. The downward Löwenheim-Skolem theorem states that G has a countable elementary sub-structure. My question is whether such sub-structure i …
12 votes
1 answer
1k views

Higman embedding theorem

The Higman Embedding theorem says that any finitely generated and recursively presented group can be embedded in a finitely presented group. My question is if one can embed such a group as a normal s …
12 votes
5 answers
4k views

What can be said about a group from its presentation?

This maybe a very general question. If we have a group given by its presentation only, what kind of properties could be proven about it? I know examples about non-amenability of some Burnside groups …
11 votes
0 answers
417 views

Topology of marked groups for different number of generators

A $k$-marked groups is a pair $(G,S)$ where $G$ is a group and $S$ is an ordered set of $k$ generators of $G$. Each such pair can be identified with a normal subgroup of the free group $F_k$ of rank $ …
7 votes
2 answers
240 views

Number of relations and free subgroups

Is there a function $f$ such that for any presentation $$G=\langle x_1,\ldots,x_n \mid r_1,\ldots,r_k\rangle\quad \text{with}\quad |r_i|\leq 3$$ $k\leq f(n)$ implies that $G$ has non-abelian free …
7 votes

Understanding groups that are not linear

If you have a finitely generated linear group whose growth is sub-exponential, then by Tits alternative (mentioned above) the group has to be virtually solvable and by a theorem of Milnor the group h …
Mustafa Gokhan Benli's user avatar
7 votes
1 answer
1k views

Examples of finitely generated elementary amenable groups which are not virtually solvable

What are some examples of finitely generated (finitely presented) elementary amenable groups which are not virtually solvable?
1 vote
Accepted

Subgroups with Infinite cyclic quotients of the Thompons's group

The first answer is incomplete and moreover I suspect that it is incorrect! Here is an answer submitted to me via email by Andrew Brunner, who asked me to post his answer for him since he is not sig …
Mustafa Gokhan Benli's user avatar
3 votes
2 answers
372 views

Subgroups with Infinite cyclic quotients of the Thompons's group

A theorem in Geoghean's book is the following (theorem 18.3.18): Let $G$ be a finitely presented group and let the rank of $G/G'$ (as a $\mathbb{Z}$-module) be at least 2. If $G$ has no non-abelian …
10 votes
3 answers
1k views

Profinite completion of a semidirect product

If we have two finitely generated residually finite groups $G$ and $H$, is there are relation between the profinite completions $\hat{G},\hat{H}$ and the profinite completion of a semidirect product …
8 votes
1 answer
529 views

Quotients of f.p. amenable groups

Can you give me an example of a finitely generated infinitely presented amenable group which is a quotient of a finitely presented amenable group?

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