Transitive subgroup of symmetric group

From Groupprops
Revision as of 16:22, 20 November 2023 by R-a-jones (talk | contribs) (→‎Examples)

This article is about a basic definition in group theory. The article text may, however, contain advanced material.
VIEW: Definitions built on this | Facts about this: (facts closely related to Transitive subgroup of symmetric group, all facts related to Transitive subgroup of symmetric group) |Survey articles about this | Survey articles about definitions built on this
VIEW RELATED: Analogues of this | Variations of this | Opposites of this |[SHOW MORE]

Definition

Let Sn be the symmetric group on n letters. Let it act naturally on X={1,2,…,n}. A subgroup G≤Sn is said to be a transitive subgroup of the symmetric group on n letters if its group action on X made from the restriction of the action of Sn on X is a transitive group action.

Examples

General facts

  • Any G≤Sn that contains an n-cycle is certainly transitive - successive applications of that cycle can send any x∈X={1,2,…,n} to any other element of X under the natural group action.
  • A partial converse of the above exists. For p prime, if G≤Sp is transitive then it must contain a p-cycle.

Small symmetric groups

n=1, n=2, symmetric groups of order 1, 2

In these cases, the symmetric group only has itself as a transitive subgroup. The symmetric group is isomorphic to the trivial group and cyclic group:Z2 respectively.

n=3, symmetric group of order 6

See also: subgroup structure of symmetric group:S3

The transitive subgroups of symmetric group:S3 are, up to automorphism classes of subgroups:

Automorphism class of subgroups List of all subgroups Isomorphism class Order of subgroups Index of subgroups Number of conjugacy classes (=1 iff automorph-conjugate subgroup) Size of each conjugacy class (=1 iff normal subgroup) Total number of subgroups (=1 iff characteristic subgroup) Isomorphism class of quotient (if exists) Note
A3 in S3 {(),(1,2,3),(1,3,2)} cyclic group:Z3 3 2 1 1 1 cyclic group:Z2 3-Sylow
whole group {(),(1,2,3),(1,3,2),
(1,2),(1,3),(2,3)}
symmetric group:S3 6 1 1 1 1 trivial group
Total (2 rows) -- -- -- -- 4 -- 6 -- --

n=4, symmetric group of order 24

See also: subgroup structure of symmetric group:S4

The transitive subgroups of symmetric group:S4 are, up to automorphism classes of subgroups:

Automorphism class of subgroups Representative Isomorphism class Order of subgroups Index of subgroups Number of conjugacy classes (=1 iff automorph-conjugate subgroup) Size of each conjugacy class (=1 iff normal subgroup) Number of subgroups (=1 iff characteristic subgroup) Isomorphism class of quotient (if exists) Subnormal depth (if subnormal) Note
Z4 in S4 ⟨(1,2,3,4)⟩ cyclic group:Z4 4 6 1 3 3 -- --
normal Klein four-subgroup of S4 {(),(1,2)(3,4),
(1,3)(2,4),(1,4)(2,3)}
Klein four-group 4 6 1 1 1 symmetric group:S3 1 2-core
D8 in S4 ⟨(1,2,3,4),(1,3)⟩ dihedral group:D8 8 3 1 3 3 -- -- 2-Sylow, fusion system is non-inner non-simple fusion system for dihedral group:D8
A4 in S4 ⟨(1,2,3),(1,2)(3,4)⟩ alternating group:A4 12 2 1 1 1 cyclic group:Z2 1
whole group ⟨(1,2,3,4),(1,2)⟩ symmetric group:S4 24 1 1 1 1 trivial group 0
Total (5 rows) -- -- -- -- 11 -- 30 -- -- --

n=5, symmetric group of order 120

Automorphism class of subgroups Representative subgroup Isomorphism class Order of subgroups Index of subgroups Number of conjugacy classes (= 1 iff automorph-conjugate subgroup) Size of each conjugacy class (= 1 iff normal subgroup) Total number of subgroups (= 1 iff characteristic subgroup)
Z5 in S5 ⟨(1,2,3,4,5)⟩ cyclic group:Z5 5 24 1 6 6 5-Sylow
D10 in S5 ⟨(1,2,3,4,5),(2,5)(3,4)⟩ dihedral group:D10 10 12 1 6 6
GA(1,5) in S5 ⟨(1,2,3,4,5),(2,3,5,4)⟩ general affine group:GA(1,5) 20 6 1 6 6
A5 in S5 ⟨(1,2,3,4,5),(1,2,3)⟩ alternating group:A5 60 2 1 1 1 only proper nontrivial normal subgroup, quotient is cyclic group:Z2
whole group ⟨(1,2,3,4,5),(1,2)⟩ symmetric group:S5 120 1 1 1 1
Total (5 rows) -- -- -- -- 19 -- 156 --