Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 28104

Questions on group theory which concern finite groups.

3 votes

Finite groups which have elements $g$ of order $pq$ such that the sizes of the conjugacy cla...

Yes, it trivially happens if $G = \langle g \rangle$ is the cyclic group of order $pq$ -- then all $3$ conjugacy classes mentioned have precisely one element. A smallest example of a nonabelian group …
Stefan Kohl's user avatar
  • 19.6k
7 votes
Accepted

Finite groups of order $n$ having exactly $n$ subgroups

There are finite groups of order $n$ having exactly $n$ subgroups for $n = 1$, $2$, $6$, $8$, $28$, $36$, $40$, $40$, $48$, $54$, $72$, $\dots$, and this list is exhaustive for $n < 96$. The structure …
Stefan Kohl's user avatar
  • 19.6k
12 votes

Perfect group of order 190080

Just write gap> G := PerfectGroup(IsPermGroup,190080); M12 2^1 in order to get the desired group as a permutation group: gap> GeneratorsOfGroup(G); [ (3,6)(7,10)(9,12)(13,16)(15,18)(19,22)(20,23)( …
Stefan Kohl's user avatar
  • 19.6k
6 votes
Accepted

Finite solvable groups with abelian Fitting subgroup

The relation between supersolvability of a finite group and its Fitting subgroup is that for a finite group $G$ the following are equivalent: $G$ is supersolvable. $G' \leq {\rm Fit}(G)$ and ${\rm F …
Stefan Kohl's user avatar
  • 19.6k
4 votes
0 answers
159 views

Can the numbers of elements of distinct prime orders of a finite simple group coincide? [duplicate]

Does there exist a finite simple group $G$ and distinct prime numbers $p$ and $q$ dividing the order of $G$ such that the numbers of elements of $G$ of order $p$ and $q$ are the same? Remark 1: It ha …
Stefan Kohl's user avatar
  • 19.6k
3 votes

Equivalence classes of (2,3)-pairs in PSL(2,q)

While your observation is true also for ${\rm PSL}(2,7)$, ${\rm PSL}(2,8)$ and ${\rm PSL}(2,9)$, it is false for ${\rm PSL}(2,11)$. -- In ${\rm PSL}(2,11)$ there are two orbits of $(2,3)$-pairs whose …
Stefan Kohl's user avatar
  • 19.6k
9 votes
Accepted

Bounding from below the cardinality of a set of generators of the $n$-fold cartesian product...

The answer is no. -- For example, ${{\rm A}_5}^3$ is $2$-generated. -- We have e.g. $$ \langle (2,5)(3,4)(6,7,8,9,10)(11,12,15), (1,3,2,4,5)(6,7,9,10,8)(11,13,12,14,15) \rangle \ \cong \ {{\rm A}_ …
Stefan Kohl's user avatar
  • 19.6k
6 votes

About the number of their conjugacy classes in some classes of finite simple groups

No, in general the numbers of conjugacy classes of $B_n(q)$ and $C_n(q)$ differ -- for example, $B_3(3)$ has $58$ conjugacy classes, while $C_3(3)$ has $74$. This can be found easily with GAP: gap> S …
Stefan Kohl's user avatar
  • 19.6k
4 votes
Accepted

Solvability of finite groups of order coprime to 15 -- proof without using CFSG?

As Derek Holt has pointed out, the answer to the question is yes. -- Thompson proved that the only finite simple groups of order coprime to 3 are the Suzuki groups, and Glauberman later extended this …
4 votes

The Frattini subgroup of $D_{\infty}$

Put $a := xy$ and $b := y$. Then we have ${\rm D}_\infty = \langle a, b \rangle$. Clearly $a$ generates a subgroup of index 2, which is thus maximal. Also, given a prime $p$, the subgroup $G_p := \lan …
Stefan Kohl's user avatar
  • 19.6k
5 votes

Groups of order $p(p^2+1)/2$

For any constant $C \in \mathbb{N}$, there are infinitely many primes $p$ such that there are at least $C$ nonabelian groups of order $p(p^2+1)/2$: Let $q \equiv 1$ mod $4$ be a prime, and $k \in \ma …
Stefan Kohl's user avatar
  • 19.6k
10 votes
Accepted

Finite groups for which the element orders form an arithmetic progression

No, your impression is not correct. -- A counterexample is the group ${\rm S}_5$, whose elements have orders $1, 2, 3, 4, 5$ and $6$. As to groups with spectrum (i.e. set of element orders) equal to …
Stefan Kohl's user avatar
  • 19.6k
4 votes
1 answer
150 views

Subgroups of finite simple groups $L(q^f)$ of Lie type normalized by $L(q)$

The following is a question asked to me these days by Gülin Ercan. Let $G = L(q^f)$ be a finite simple group of Lie type, and let $L(q) \cong H \le G$ be the group of fixed points of the automorphisms …
Stefan Kohl's user avatar
  • 19.6k
8 votes
1 answer
462 views

Solvability of finite groups of order coprime to 15 -- proof without using CFSG?

Is the solvability of finite groups of order coprime to 15 essentially easier to prove than the entire Classification of Finite Simple Groups?
Stefan Kohl's user avatar
  • 19.6k
2 votes

Orders of finite 2-simple groups

At least four such groups can share the same order: $$ |{\rm A}_7 \times {\rm PSp}(6,2)| = |{\rm PSU}(3,3) \times {\rm J}_2| = |{\rm A}_8 \times {\rm A}_9| = |{\rm PSL}(3,4) \times {\rm A}_9| …
Stefan Kohl's user avatar
  • 19.6k

15 30 50 per page