Difference between revisions of "Symmetric group:S5"

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(Endomorphisms)
(Endomorphisms)
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==Endomorphisms==
 
==Endomorphisms==
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{{further|[[endomorphism structure of symmetric group:S5]]}}
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===Summary information===
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{{#lst:endomorphism structure of symmetric group:S5|summary}}
  
 
===Automorphisms===
 
===Automorphisms===
  
Since <math>S_5</math> is a complete group, it is isomorphic to its automorphism group, where each element of <math>S_5</math> acts on <math>S_5</math> by conjugation.
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Since <math>S_5</math> is a complete group, it is isomorphic to its automorphism group, where each element of <math>S_5</math> acts on <math>S_5</math> by conjugation. {{further|[[symmetric groups on finite sets are complete]]}}
  
 
==Subgroups==
 
==Subgroups==

Revision as of 17:28, 1 October 2011

This article is about a particular group, i.e., a group unique upto isomorphism. View specific information (such as linear representation theory, subgroup structure) about this group
View a complete list of particular groups (this is a very huge list!)[SHOW MORE]

Definition

The symmetric group S_5 is defined in the following equivalent ways:

Presentation

Arithmetic functions

Want to compare and contrast arithmetic function values with other groups of the same order? Check out groups of order 120#Arithmetic functions
Function Value Similar groups Explanation
order (number of elements, equivalently, cardinality or size of underlying set) 120 groups with same order As \! S_k, k = 5: \! 5! = 5 \cdot 4 \cdot 3 \cdot 2 \cdot 1 = 120

As \! PGL(2,q), q  = 5: (q^2 - 1)(q^2 - q)/(q - 1) = (5^2 - 1)(5^2 - 5)/(5 - 1) = (24 \cdot 20)/4 = 120
exponent 60 groups with same order and exponent | groups with same exponent As \! S_k, k = 5: \! \operatorname{lcm} \{1,2,3,4,5 \} = 60

As \! PGL(2,q), q = p = 5: (where \! p is the underlying prime for \! q) \! p(q^2 - 1)/2 = 5 \cdot (5^2 - 1)/2 = 60
derived length -- not a solvable group.
nilpotency class -- not a nilpotent group.
Frattini length 1 groups with same order and Frattini length | groups with same Frattini length Frattini-free group: intersection of maximal subgroups is trivial.
minimum size of generating set 2 groups with same order and minimum size of generating set | groups with same minimum size of generating set \! (1,2), (1,2,3,4,5); see also symmetric group on a finite set is 2-generated
subgroup rank of a group 2 groups with same order and subgroup rank of a group | groups with same subgroup rank of a group
max-length of a group 5 groups with same order and max-length of a group | groups with same max-length of a group
number of subgroups 156 groups with same order and number of subgroups | groups with same number of subgroups
number of conjugacy classes 7 groups with same order and number of conjugacy classes | groups with same number of conjugacy classes As \! S_k, k = 5: the number of conjugacy classes is \! p(k) = p(5) = 7, where p is the number of unordered integer partitions. See also cycle type determines conjugacy class

As \! PGL(2,q), q = 5: \! q + 2 = 5 + 2 = 7
number of conjugacy classes of subgroups 19 groups with same order and number of conjugacy classes of subgroups | groups with same number of conjugacy classes of subgroups

Group properties

COMPARE AND CONTRAST: Want to know more about how this group compares with symmetric groups of other degrees? Read contrasting symmetric groups of various degrees.
Property Satisfied? Explanation Comment
Abelian group No (1,2), (1,3) don't commute S_n is non-abelian, n \ge 3.
Nilpotent group No Centerless: The center is trivial S_n is non-nilpotent, n \ge 3.
Metacyclic group No No cyclic normal subgroup S_n is not metacyclic, n \ge 4.
Supersolvable group No No cyclic normal subgroup S_n is not supersolvable, n \ge 4.
Solvable group No The subgroup A_5 is simple non-abelian A_n is simple and hence S_n not solvable, n \ge 5.
T-group Yes
HN-group Yes
Complete group Yes Centerless and every automorphism's inner Symmetric groups are complete except the ones of degree 2,6.
Monolithic group Yes Monolith is the alternating group All symmetric groups are monolithic; n=4 is the only case the monolith is not the alternating group.
One-headed group Yes The alternating group is the unique maximal normal subgroup True for all n > 1.

Elements

Further information: element structure of symmetric group:S5

Upto conjugacy

For convenience, we take the underlying set to be \{ 1,2,3,4,5 \}.

There are seven conjugacy classes, corresponding to the unordered integer partitions of 5 (for more information, refer cycle type determines conjugacy class). We use the notation of the cycle decomposition for permutations:


Partition Partition in grouped form Verbal description of cycle type Representative element with the cycle type Size of conjugacy class Formula calculating size Even or odd? If even, splits? If splits, real in alternating group? Element order Formula calcuating element order
1 + 1 + 1 + 1 + 1 1 (5 times) five fixed points () -- the identity element 1 \! \frac{5!}{(1)^5(5!)} even; no 1 \operatorname{lcm}\{1 \}
2 + 1 + 1 + 1 2 (1 time), 1 (3 times) transposition: one 2-cycle, three fixed point (1,2) 10 \! \frac{5!}{[(2)^1(1!)][(1)^3(3!)]} or \! \frac{5!}{(2)(1)^3(3!)}, also \binom{5}{2} in this case odd 2 \operatorname{lcm}\{2,1 \}
3 + 1 + 1 3 (1 time), 1 (2 times) one 3-cycle, two fixed points (1,2,3) 20 \! \frac{5!}{[(3)^1(1!)][(1)^2(2!)]} or \! \frac{5!}{(3)(1)^2(2!)} even; no 3 \operatorname{lcm}\{3,1\}
2 + 2 + 1 2 (2 times), 1 (1 time) double transposition: two 2-cycles, one fixed point (1,2)(3,4) 15 \frac{5!}{[2^2(2!)][1^1(1!)]} or \! \frac{5!}{2^2(2!)(1)} even; no 2 \operatorname{lcm}\{2,1 \}
4 + 1 4 (1 time), 1 (1 time) one 4-cycle, one fixed point (1,2,3,4) 30 \! \frac{5!}{[4^1(1!)][1^1(1!)]} or\! \frac{5!}{(4)(1)} odd 4 \operatorname{lcm}\{4,1\}
3 + 2 3 (1 time), 2 (1 time) one 3-cycle, one 2-cycle (1,2,3)(4,5) 20 \! \frac{5!}{[3^1(1!)][2^1(1!)]} or \! \frac{5!}{(3)(2)} odd 6 \operatorname{lcm}\{3,2 \}
5 5 (1 time) one 5-cycle (1,2,3,4,5) 24 \frac{5!}{5^1(1!)} or \! \frac{5!}{5} even; yes; yes 5 \operatorname{lcm} \{ 5 \}
Total (7 rows, 7 being the number of unordered integer partitions of 5) -- -- -- 120 (equals order of the group) -- odd: 60 (3 classes)
even;no: 36 (3 classes)
even;yes;yes: 24 (1 class)
[SHOW MORE]


Upto automorphism

S_5 is a complete group: in particular, every automorphism of the group is inner. Thus, the equivalence classes under automorphisms are the same as the conjugacy classes. In fact, S_n is complete for n \ne 2, 6. See symmetric groups on finite sets are complete.

Endomorphisms

Further information: endomorphism structure of symmetric group:S5

Summary information

Construct Value Order Second part of GAP ID (if group)
endomorphism monoid  ? 146 --
automorphism group symmetric group:S5 120 34
inner automorphism group symmetric group:S5 120 34
extended automorphism group direct product of S5 and Z2 240 189


Automorphisms

Since S_5 is a complete group, it is isomorphic to its automorphism group, where each element of S_5 acts on S_5 by conjugation. Further information: symmetric groups on finite sets are complete

Subgroups

Further information: Subgroup structure of symmetric group:S5

GAP implementation

Group ID

This finite group has order 120 and has ID 34 among the groups of order 120 in GAP's SmallGroup library. For context, there are 47 groups of order 120. It can thus be defined using GAP's SmallGroup function as:

SmallGroup(120,34)

For instance, we can use the following assignment in GAP to create the group and name it G:

gap> G := SmallGroup(120,34);

Conversely, to check whether a given group G is in fact the group we want, we can use GAP's IdGroup function:

IdGroup(G) = [120,34]

or just do:

IdGroup(G)

to have GAP output the group ID, that we can then compare to what we want.


Other descriptions

Description Functions used
SymmetricGroup(5) SymmetricGroup
PGL(2,5) PGL