All permutations carrying the set {1,2} into the set {1,2}












0












$begingroup$


Book question:




Describe the following subgroups of $S_4$ and determine the number of elements in each subgroup:



a) All permutations carrying the set {1,2} into the set {1,2}




My question:




What does it mean by carrying the set {1,2} into the set {1,2}?




I assume it means permutations such as (12) and (12)(34), but would it also include (123) (which I sort of doubt because 2 $rightarrow$ 3 and 3 $notin$ {1,2}) or permutations where 1 and 2 don't permute, such as (34) = (1)(2)(34)?










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$endgroup$












  • $begingroup$
    I'm sure it means the $sigmain S_4$ with $sigma(A)=A$ where $A={1,2}$. Also, please see math.meta.stackexchange.com/questions/5020
    $endgroup$
    – Lord Shark the Unknown
    Nov 5 '18 at 6:40
















0












$begingroup$


Book question:




Describe the following subgroups of $S_4$ and determine the number of elements in each subgroup:



a) All permutations carrying the set {1,2} into the set {1,2}




My question:




What does it mean by carrying the set {1,2} into the set {1,2}?




I assume it means permutations such as (12) and (12)(34), but would it also include (123) (which I sort of doubt because 2 $rightarrow$ 3 and 3 $notin$ {1,2}) or permutations where 1 and 2 don't permute, such as (34) = (1)(2)(34)?










share|cite|improve this question











$endgroup$












  • $begingroup$
    I'm sure it means the $sigmain S_4$ with $sigma(A)=A$ where $A={1,2}$. Also, please see math.meta.stackexchange.com/questions/5020
    $endgroup$
    – Lord Shark the Unknown
    Nov 5 '18 at 6:40














0












0








0





$begingroup$


Book question:




Describe the following subgroups of $S_4$ and determine the number of elements in each subgroup:



a) All permutations carrying the set {1,2} into the set {1,2}




My question:




What does it mean by carrying the set {1,2} into the set {1,2}?




I assume it means permutations such as (12) and (12)(34), but would it also include (123) (which I sort of doubt because 2 $rightarrow$ 3 and 3 $notin$ {1,2}) or permutations where 1 and 2 don't permute, such as (34) = (1)(2)(34)?










share|cite|improve this question











$endgroup$




Book question:




Describe the following subgroups of $S_4$ and determine the number of elements in each subgroup:



a) All permutations carrying the set {1,2} into the set {1,2}




My question:




What does it mean by carrying the set {1,2} into the set {1,2}?




I assume it means permutations such as (12) and (12)(34), but would it also include (123) (which I sort of doubt because 2 $rightarrow$ 3 and 3 $notin$ {1,2}) or permutations where 1 and 2 don't permute, such as (34) = (1)(2)(34)?







abstract-algebra terminology permutation-cycles






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 24 '18 at 18:58









Shaun

9,083113683




9,083113683










asked Nov 5 '18 at 6:31









JayJay

11




11












  • $begingroup$
    I'm sure it means the $sigmain S_4$ with $sigma(A)=A$ where $A={1,2}$. Also, please see math.meta.stackexchange.com/questions/5020
    $endgroup$
    – Lord Shark the Unknown
    Nov 5 '18 at 6:40


















  • $begingroup$
    I'm sure it means the $sigmain S_4$ with $sigma(A)=A$ where $A={1,2}$. Also, please see math.meta.stackexchange.com/questions/5020
    $endgroup$
    – Lord Shark the Unknown
    Nov 5 '18 at 6:40
















$begingroup$
I'm sure it means the $sigmain S_4$ with $sigma(A)=A$ where $A={1,2}$. Also, please see math.meta.stackexchange.com/questions/5020
$endgroup$
– Lord Shark the Unknown
Nov 5 '18 at 6:40




$begingroup$
I'm sure it means the $sigmain S_4$ with $sigma(A)=A$ where $A={1,2}$. Also, please see math.meta.stackexchange.com/questions/5020
$endgroup$
– Lord Shark the Unknown
Nov 5 '18 at 6:40










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