a normal k-1 transitive subgroup











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I want to show that if G is k-transitive and N is a normal nontrivial subgroup then is K-1 transitive.
I know that I should use the fact G preserve the orbit of N's action of X. so for some Y on N's action, gY is an orbit of N's action on X.
Any help is appreciated.










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    up vote
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    down vote

    favorite












    I want to show that if G is k-transitive and N is a normal nontrivial subgroup then is K-1 transitive.
    I know that I should use the fact G preserve the orbit of N's action of X. so for some Y on N's action, gY is an orbit of N's action on X.
    Any help is appreciated.










    share|cite|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I want to show that if G is k-transitive and N is a normal nontrivial subgroup then is K-1 transitive.
      I know that I should use the fact G preserve the orbit of N's action of X. so for some Y on N's action, gY is an orbit of N's action on X.
      Any help is appreciated.










      share|cite|improve this question













      I want to show that if G is k-transitive and N is a normal nontrivial subgroup then is K-1 transitive.
      I know that I should use the fact G preserve the orbit of N's action of X. so for some Y on N's action, gY is an orbit of N's action on X.
      Any help is appreciated.







      group-theory






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      asked Nov 16 at 19:49









      N3d4

      102




      102






















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          You won't be able to show it, because it is not true. For example $S_4$ is $4$-transitive, but has a normal subgroup of order $4$, which is only $1$-transitive.



          More generally, for all $n ge 2$, there is a group ${rm AGL}(n,2)$ of degree $2^n$ which is $3$-transitive but has a normal subgroup of order $2^n$ which is only $1$-transitive. (The case $n=2$ gives $S_4$.)






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          • Thank you. But it is an exersise from book. So I think I can show it. I forgot to mention K>2.
            – N3d4
            Nov 17 at 5:51












          • As I said, $S_4$ is clearly a counterexample with $k=4$, so how can you possibly show it? Exercises in books can be wrong.
            – Derek Holt
            Nov 17 at 8:39













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          1 Answer
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          1 Answer
          1






          active

          oldest

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          active

          oldest

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          active

          oldest

          votes








          up vote
          3
          down vote



          accepted










          You won't be able to show it, because it is not true. For example $S_4$ is $4$-transitive, but has a normal subgroup of order $4$, which is only $1$-transitive.



          More generally, for all $n ge 2$, there is a group ${rm AGL}(n,2)$ of degree $2^n$ which is $3$-transitive but has a normal subgroup of order $2^n$ which is only $1$-transitive. (The case $n=2$ gives $S_4$.)






          share|cite|improve this answer





















          • Thank you. But it is an exersise from book. So I think I can show it. I forgot to mention K>2.
            – N3d4
            Nov 17 at 5:51












          • As I said, $S_4$ is clearly a counterexample with $k=4$, so how can you possibly show it? Exercises in books can be wrong.
            – Derek Holt
            Nov 17 at 8:39

















          up vote
          3
          down vote



          accepted










          You won't be able to show it, because it is not true. For example $S_4$ is $4$-transitive, but has a normal subgroup of order $4$, which is only $1$-transitive.



          More generally, for all $n ge 2$, there is a group ${rm AGL}(n,2)$ of degree $2^n$ which is $3$-transitive but has a normal subgroup of order $2^n$ which is only $1$-transitive. (The case $n=2$ gives $S_4$.)






          share|cite|improve this answer





















          • Thank you. But it is an exersise from book. So I think I can show it. I forgot to mention K>2.
            – N3d4
            Nov 17 at 5:51












          • As I said, $S_4$ is clearly a counterexample with $k=4$, so how can you possibly show it? Exercises in books can be wrong.
            – Derek Holt
            Nov 17 at 8:39















          up vote
          3
          down vote



          accepted







          up vote
          3
          down vote



          accepted






          You won't be able to show it, because it is not true. For example $S_4$ is $4$-transitive, but has a normal subgroup of order $4$, which is only $1$-transitive.



          More generally, for all $n ge 2$, there is a group ${rm AGL}(n,2)$ of degree $2^n$ which is $3$-transitive but has a normal subgroup of order $2^n$ which is only $1$-transitive. (The case $n=2$ gives $S_4$.)






          share|cite|improve this answer












          You won't be able to show it, because it is not true. For example $S_4$ is $4$-transitive, but has a normal subgroup of order $4$, which is only $1$-transitive.



          More generally, for all $n ge 2$, there is a group ${rm AGL}(n,2)$ of degree $2^n$ which is $3$-transitive but has a normal subgroup of order $2^n$ which is only $1$-transitive. (The case $n=2$ gives $S_4$.)







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Nov 16 at 21:34









          Derek Holt

          52k53468




          52k53468












          • Thank you. But it is an exersise from book. So I think I can show it. I forgot to mention K>2.
            – N3d4
            Nov 17 at 5:51












          • As I said, $S_4$ is clearly a counterexample with $k=4$, so how can you possibly show it? Exercises in books can be wrong.
            – Derek Holt
            Nov 17 at 8:39




















          • Thank you. But it is an exersise from book. So I think I can show it. I forgot to mention K>2.
            – N3d4
            Nov 17 at 5:51












          • As I said, $S_4$ is clearly a counterexample with $k=4$, so how can you possibly show it? Exercises in books can be wrong.
            – Derek Holt
            Nov 17 at 8:39


















          Thank you. But it is an exersise from book. So I think I can show it. I forgot to mention K>2.
          – N3d4
          Nov 17 at 5:51






          Thank you. But it is an exersise from book. So I think I can show it. I forgot to mention K>2.
          – N3d4
          Nov 17 at 5:51














          As I said, $S_4$ is clearly a counterexample with $k=4$, so how can you possibly show it? Exercises in books can be wrong.
          – Derek Holt
          Nov 17 at 8:39






          As I said, $S_4$ is clearly a counterexample with $k=4$, so how can you possibly show it? Exercises in books can be wrong.
          – Derek Holt
          Nov 17 at 8:39




















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