Nontrivial conjugacy class and simplicity











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Prove that if $G$ has a nontrivial conjugacy class $K$ such that $|G|$ does not divide $|K|!$, then $G$ is not simple.




How can I prove this statement? I think that with the condition, I could find nontrivial normal subgroup. But I failed. Help me!










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    Hint: $G$ acts non-trivially on $K$.
    – Tobias Kildetoft
    yesterday










  • @TobiasKildetoft Thank you. I solve it!
    – Pearl
    yesterday















up vote
0
down vote

favorite













Prove that if $G$ has a nontrivial conjugacy class $K$ such that $|G|$ does not divide $|K|!$, then $G$ is not simple.




How can I prove this statement? I think that with the condition, I could find nontrivial normal subgroup. But I failed. Help me!










share|cite|improve this question




















  • 4




    Hint: $G$ acts non-trivially on $K$.
    – Tobias Kildetoft
    yesterday










  • @TobiasKildetoft Thank you. I solve it!
    – Pearl
    yesterday













up vote
0
down vote

favorite









up vote
0
down vote

favorite












Prove that if $G$ has a nontrivial conjugacy class $K$ such that $|G|$ does not divide $|K|!$, then $G$ is not simple.




How can I prove this statement? I think that with the condition, I could find nontrivial normal subgroup. But I failed. Help me!










share|cite|improve this question
















Prove that if $G$ has a nontrivial conjugacy class $K$ such that $|G|$ does not divide $|K|!$, then $G$ is not simple.




How can I prove this statement? I think that with the condition, I could find nontrivial normal subgroup. But I failed. Help me!







abstract-algebra group-theory






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edited yesterday









GNUSupporter 8964民主女神 地下教會

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asked yesterday









Pearl

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  • 4




    Hint: $G$ acts non-trivially on $K$.
    – Tobias Kildetoft
    yesterday










  • @TobiasKildetoft Thank you. I solve it!
    – Pearl
    yesterday














  • 4




    Hint: $G$ acts non-trivially on $K$.
    – Tobias Kildetoft
    yesterday










  • @TobiasKildetoft Thank you. I solve it!
    – Pearl
    yesterday








4




4




Hint: $G$ acts non-trivially on $K$.
– Tobias Kildetoft
yesterday




Hint: $G$ acts non-trivially on $K$.
– Tobias Kildetoft
yesterday












@TobiasKildetoft Thank you. I solve it!
– Pearl
yesterday




@TobiasKildetoft Thank you. I solve it!
– Pearl
yesterday










1 Answer
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Consider the group $G$ act on $K$ via conjugation.



Then by such homomorphism $phi$, with 1st isomorphism theorem, $|G/Kerphi|||K|!$



If $Kerphi={1}$, it contradicts the non-divisibility condition in problem.



If $Kerphi=G$, it contradicts the nontriviality of conjugacy class $K$.



So we get nontrivial normal subgroup $Kerphi$ which shows that G is not simple.






share|cite|improve this answer





















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    1 Answer
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    1 Answer
    1






    active

    oldest

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    oldest

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    active

    oldest

    votes








    up vote
    0
    down vote



    accepted










    Consider the group $G$ act on $K$ via conjugation.



    Then by such homomorphism $phi$, with 1st isomorphism theorem, $|G/Kerphi|||K|!$



    If $Kerphi={1}$, it contradicts the non-divisibility condition in problem.



    If $Kerphi=G$, it contradicts the nontriviality of conjugacy class $K$.



    So we get nontrivial normal subgroup $Kerphi$ which shows that G is not simple.






    share|cite|improve this answer

























      up vote
      0
      down vote



      accepted










      Consider the group $G$ act on $K$ via conjugation.



      Then by such homomorphism $phi$, with 1st isomorphism theorem, $|G/Kerphi|||K|!$



      If $Kerphi={1}$, it contradicts the non-divisibility condition in problem.



      If $Kerphi=G$, it contradicts the nontriviality of conjugacy class $K$.



      So we get nontrivial normal subgroup $Kerphi$ which shows that G is not simple.






      share|cite|improve this answer























        up vote
        0
        down vote



        accepted







        up vote
        0
        down vote



        accepted






        Consider the group $G$ act on $K$ via conjugation.



        Then by such homomorphism $phi$, with 1st isomorphism theorem, $|G/Kerphi|||K|!$



        If $Kerphi={1}$, it contradicts the non-divisibility condition in problem.



        If $Kerphi=G$, it contradicts the nontriviality of conjugacy class $K$.



        So we get nontrivial normal subgroup $Kerphi$ which shows that G is not simple.






        share|cite|improve this answer












        Consider the group $G$ act on $K$ via conjugation.



        Then by such homomorphism $phi$, with 1st isomorphism theorem, $|G/Kerphi|||K|!$



        If $Kerphi={1}$, it contradicts the non-divisibility condition in problem.



        If $Kerphi=G$, it contradicts the nontriviality of conjugacy class $K$.



        So we get nontrivial normal subgroup $Kerphi$ which shows that G is not simple.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered yesterday









        user347643

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