All Questions
Tagged with combinatorial-group-theory finite-groups
22 questions
2
votes
1
answer
339
views
Proving certain triangle groups are infinite
[Cross-posted from MSE]
Consider the Von Dyck group
$$ G = \langle x,y\mid x^a=y^b=(xy)^c=1\rangle $$
where $a,b,c\ge3$. Because $G$ is infinite and residually finite, it has an infinite family of ...
- 4,425
5
votes
0
answers
199
views
Finite groups with number of generators strictly less than number of relations
For the finite cyclic group of order $n$, there is the standard presentation $\langle a \mid a^n\rangle$. Also for $S_n$ (symmetric group), I know a few presentations where the number of relations is ...
- 179
5
votes
1
answer
386
views
Is this semi-direct product residually finite?
I've copied over this question from what I asked on Mathematics Stack Exchange, in the hope that some experts here can help me find a way to check the residual finiteness of this group.
Consider the ...
- 823
2
votes
2
answers
309
views
Combinatorial problem in $G(32, \, 6)$
The following problem arose when studying the same type of questions in Algebraic Geometry that led me to my previous question MO379272.
Let us consider the group $G$ of order $32$ whose label in GAP4 ...
- 66.3k
2
votes
1
answer
656
views
Combinatorial problem in $\mathsf{S}_4$
I am working on a problem in Combinatorial Group Theory related to a construction in Algebraic Geometry, and I would like to have a conceptual proof of the fact described below.
I am looking for ...
- 66.3k
2
votes
1
answer
233
views
Proving an inequality regarding number of transitive subgroups of the symmetric group
I defined the sequence $t$ where where $t(n)$ is the number of transitive subgroups of $S_n$ where we regard conjugate subgroups as distinct, i.e. the labeled version of A002106 at the OEIS.
Then I ...
4
votes
2
answers
228
views
CCT groups of order $\leq 32$
A finite, non-abelian group $G$ is said to be a center
commutative-transitive group
$($or a CCT-group, for short$)$ if commutativity is a transitive
relation on the set on non-central elements. In ...
- 66.3k
7
votes
0
answers
420
views
Are these two kernels isomorphic groups?
We have a finitely presented, infinite group $\mathsf{B}$,
coming from a geometric topology problem (it is the quotient of a braid group for a genus 2 surface).
It is generated by elements
\begin{...
- 66.3k
1
vote
0
answers
21
views
Do small subsets of $S_n$ subgroups cover almost all permutation configurations of $S_n$?
Given integer $m\in[1,n]$ fix a set $\mathcal T$ of permutations in $S_n$. Then there are subgroups $G_1,\dots,G_m$ of $S_n$ so that $\mathcal T$ is covered by cosets of $G_1,\dots,G_m$.
For ...
- 13.9k
1
vote
0
answers
92
views
Are almost all permutation configurations from $S_n$ covered by small subsets subgroups of $S_n$?
Given integer $m\in[1,n]$ fix a set $\mathcal T$ of permutations in $S_n$. Then there are subgroups $G_1,\dots,G_m$ of $S_n$ so that $\mathcal T$ is covered by cosets of $G_1,\dots,G_m$.
Do we have ...
- 13.9k
9
votes
0
answers
310
views
Breuer-Guralnick-Kantor conjecture and infinite 3/2-generated groups
A group $G$ is called $\frac{3}{2}$-generated if every non-trivial element is contained in a generating pair, i.e. $$\forall g \in G \setminus \{e \}, \ \exists g' \in G \text{ such that } \langle g,g'...
3
votes
1
answer
501
views
When is the semidirect product of $(Z/pZ)^n$ and $(Z/qZ)^2$ generated by two elements?
I asked a very similar question here and got a wonderful answer. But now I need to change the question slightly (this is the last question like this, I promise).
I would like to characterize when $(\...
- 2,720
10
votes
1
answer
1k
views
When is the semidirect product of an elementary abelian group and a cyclic group generated by two elements?
I am trying to characterize when a semi-direct product of the form $(Z/pZ)^n \rtimes (Z/qZ)$ is isomorphic to a group generated by two elements. Here $p$ and $q$ are distinct odd primes.
I would be ...
- 2,720
1
vote
4
answers
537
views
Are the orders of the generators of a group and the product of pairs of thereof enough for this group to be isomorphic to a Coxeter group?
Let's say we have $n$ generators $x_1, x_2, \cdots, x_n$ along with the following facts concerning their orders:
\begin{eqnarray*}
ord(x_i) &=& 2 \text{ for } i = 1, 2, \cdots, n \\
ord(x_i ...
user76098
10
votes
2
answers
815
views
Paper by I. N. Sanov, Solution of the Burnside problem for exponent 4
I have searched extensively online and for copies of printed journals containing the paper which details Sanov's solution to the Burnside Problem for exponent 4, which is widely cited in many papers ...
- 201
4
votes
2
answers
1k
views
Cyclic subgroups of finite abelian groups
I learned from MO Subgroups of a finite abelian group that the problem of enumerating subgroups (not up to isomorphism) of finite abelian groups is a difficult one.
Are there simple formulas if one ...
- 43
4
votes
1
answer
2k
views
Minimal generation for finite abelian groups
Let $G$ be a finite abelian group. I know of two ways of writing it as a direct sum of cyclic groups:
1) With orders $d_1, d_2, \ldots, d_k$ in such a way that $d_i|d_{i+1}$,
2) With orders that are ...
- 125
5
votes
1
answer
2k
views
For what finite groups is the cardinality of a minimal generating set well defined?
Recently I learned that the cardinality of a minimal set of generators of a finite $p$-group
$G$ is well defined namely it is equal to the dimension of $H^1(G,\mathbb{F}_p)$. Moreover, if
$S:=\{g_1,\...
- 7,609
5
votes
2
answers
703
views
infinite group that maps onto dihedral group
The group is generated by $y_i$, $i=0, ...,p-1$
with relations
$y_0y_1=y_1y_2=...=y_{p-1}y_0$
$y_0y_2=y_1y_3=...=y_{p-1}y_1$
$\vdots$
$y_0y_{p-1}=y_1y_0=...y_{p-1}y_{p-2}$
I have run into this ...
- 143
7
votes
2
answers
751
views
Looking for deterministic criteria to generate the symmetric group?
So let $S_N$ be the symmetric group of degree $N$. We think of it as a permutation group via its
natural action on the set $T=\{1,2,\ldots,N\}$.
Say that $H\leq S_N$ is a subgroup which acts ...
- 7,609
21
votes
0
answers
578
views
Density of first-order definable sets in a directed union of finite groups
This is a generalization of the following question by John Wiltshire-Gordon.
Consider an inductive family of finite groups:
$$
G_0 \hookrightarrow G_1 \hookrightarrow \ldots \hookrightarrow G_i \...
- 2,200
23
votes
3
answers
1k
views
In an inductive family of groups, does the probability that a particular word is satisfied converge?
We have some group word $w$ in $k$ letters. We say a $k$-tuple of group elements $\vec{g} = (g_1, g_2, \ldots , g_k) \in G^k$ satisfies the word $w$ if $w$ gives the identity at $\vec{g}$. More ...
- 5,898