Symmetric group:S6

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This particular group is a finite group of order: 720

Definition

The symmetric group S6, called the symmetric group of degree six, is defined as the symmetric group on a set of size six. Other equivalent definitions include:

Elements

Upto conjugacy

For convenience, we take the underlying set here as {1,2,3,4,5,6}.

There are eleven conjugacy classes, corresponding to the unordered integer partitions of 6 (for more information, refer cycle type determines conjugacy class):

  1. 6=1+1+1+1+1+1, i.e., six cycles of size one: The identity element. (1)
  2. 6=2+1+1+1+1, i.e., one 2-cycle and four fixed points: The transpositions, such as (1,2). (15)
  3. 6=3+1+1+1, i.e., one 3-cycle and three fixed points: The 3-cycles, such as (1,2,3). (40)
  4. 6=4+1+1: The 4-cycles, such as (1,2,3,4). (90)
  5. 6=5+1: The 5-cycles, such as (1,2,3,4,5). (144)
  6. 6=6: The 6-cycles, such as (1,2,3,4,5,6). (120)
  7. 6=2+2+1+1, i.e., two 2-cycles, two fixed points: The double transpositions, such as (1,2)(3,4). (45)
  8. 6=2+2+2, i.e., three 2-cycles: The triple transpositions, such as (1,2)(3,4)(5,6). (15)
  9. 6=3+2+1, i.e., one 3-cycle, one 2-cycle: Permutations such as (1,2,3)(4,5).(120)
  10. 6=3+3, i.e., two 3-cycles: Permutations such as (1,2,3)(4,5,6). (40)
  11. 6=4+2: Permutations such as (1,2,3,4)(5,6). (90)

Upto automorphism

Under automorphisms, the following types get merged:

  • Types (2) and (8): The transposition (1,2) is related by an outer automorphism to the triple transposition (1,2)(3,4)(5,6).
  • Types (3) and (10): The 3-cycle (1,2,3) is related by an outer automorphism to the permutation (1,2,3)(4,5,6).
  • Types (4) and (11): The 4-cycle (1,2,3,4) is related by an outer automorphism to the pemrutation (1,2,3,4)(5,6).
  • Types (6) and (9): The 6-cycle (1,2,3,4,5,6) is related by an outer automorphism to the permutation (1,2,3)(4,5).

The types (1), (5), and (7) remain unaffected: these conjugacy classes are also automorphism classes.