Finding element of order in the symmetric group












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What is the proper and technical way to find if there exists an element in the symmetric group $S_n$ (Wikipedia article on symmetric groups.). I do know how to disprove if there does not exists such elements, but how should I find the element which does exists of this order?



For example, in the $S_{12}$, there is not such element of order $13$ because The only elements of order $13$ in $S_n$ are unions of disjoint $13$-cycles, since $13$ is prime. This would require $S_{12}$ to contain at least $13$ symbols, which it does not. But I think that there is an element of order $35$ in $S_{12}$. How should I find it?



EDIT: I do understand that I have to find a $7$-cycle and a $5$-cycle, but how?










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  • $begingroup$
    $35=5times 7$.
    $endgroup$
    – Lord Shark the Unknown
    Jan 1 at 15:02










  • $begingroup$
    First, prove that the order of an element in $S_n$ equals the least common multiple of the lengths of the cycles in its cycle decomposition. Hence, by the answer provided by @Ross, you can prove your claim.
    $endgroup$
    – toric_actions
    Jan 1 at 15:16
















3












$begingroup$


What is the proper and technical way to find if there exists an element in the symmetric group $S_n$ (Wikipedia article on symmetric groups.). I do know how to disprove if there does not exists such elements, but how should I find the element which does exists of this order?



For example, in the $S_{12}$, there is not such element of order $13$ because The only elements of order $13$ in $S_n$ are unions of disjoint $13$-cycles, since $13$ is prime. This would require $S_{12}$ to contain at least $13$ symbols, which it does not. But I think that there is an element of order $35$ in $S_{12}$. How should I find it?



EDIT: I do understand that I have to find a $7$-cycle and a $5$-cycle, but how?










share|cite|improve this question











$endgroup$












  • $begingroup$
    $35=5times 7$.
    $endgroup$
    – Lord Shark the Unknown
    Jan 1 at 15:02










  • $begingroup$
    First, prove that the order of an element in $S_n$ equals the least common multiple of the lengths of the cycles in its cycle decomposition. Hence, by the answer provided by @Ross, you can prove your claim.
    $endgroup$
    – toric_actions
    Jan 1 at 15:16














3












3








3


1



$begingroup$


What is the proper and technical way to find if there exists an element in the symmetric group $S_n$ (Wikipedia article on symmetric groups.). I do know how to disprove if there does not exists such elements, but how should I find the element which does exists of this order?



For example, in the $S_{12}$, there is not such element of order $13$ because The only elements of order $13$ in $S_n$ are unions of disjoint $13$-cycles, since $13$ is prime. This would require $S_{12}$ to contain at least $13$ symbols, which it does not. But I think that there is an element of order $35$ in $S_{12}$. How should I find it?



EDIT: I do understand that I have to find a $7$-cycle and a $5$-cycle, but how?










share|cite|improve this question











$endgroup$




What is the proper and technical way to find if there exists an element in the symmetric group $S_n$ (Wikipedia article on symmetric groups.). I do know how to disprove if there does not exists such elements, but how should I find the element which does exists of this order?



For example, in the $S_{12}$, there is not such element of order $13$ because The only elements of order $13$ in $S_n$ are unions of disjoint $13$-cycles, since $13$ is prime. This would require $S_{12}$ to contain at least $13$ symbols, which it does not. But I think that there is an element of order $35$ in $S_{12}$. How should I find it?



EDIT: I do understand that I have to find a $7$-cycle and a $5$-cycle, but how?







group-theory permutations






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share|cite|improve this question













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edited Jan 1 at 15:09









Shaun

8,820113681




8,820113681










asked Jan 1 at 14:59









vesiivesii

886




886












  • $begingroup$
    $35=5times 7$.
    $endgroup$
    – Lord Shark the Unknown
    Jan 1 at 15:02










  • $begingroup$
    First, prove that the order of an element in $S_n$ equals the least common multiple of the lengths of the cycles in its cycle decomposition. Hence, by the answer provided by @Ross, you can prove your claim.
    $endgroup$
    – toric_actions
    Jan 1 at 15:16


















  • $begingroup$
    $35=5times 7$.
    $endgroup$
    – Lord Shark the Unknown
    Jan 1 at 15:02










  • $begingroup$
    First, prove that the order of an element in $S_n$ equals the least common multiple of the lengths of the cycles in its cycle decomposition. Hence, by the answer provided by @Ross, you can prove your claim.
    $endgroup$
    – toric_actions
    Jan 1 at 15:16
















$begingroup$
$35=5times 7$.
$endgroup$
– Lord Shark the Unknown
Jan 1 at 15:02




$begingroup$
$35=5times 7$.
$endgroup$
– Lord Shark the Unknown
Jan 1 at 15:02












$begingroup$
First, prove that the order of an element in $S_n$ equals the least common multiple of the lengths of the cycles in its cycle decomposition. Hence, by the answer provided by @Ross, you can prove your claim.
$endgroup$
– toric_actions
Jan 1 at 15:16




$begingroup$
First, prove that the order of an element in $S_n$ equals the least common multiple of the lengths of the cycles in its cycle decomposition. Hence, by the answer provided by @Ross, you can prove your claim.
$endgroup$
– toric_actions
Jan 1 at 15:16










2 Answers
2






active

oldest

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4












$begingroup$

If you want an element of order $k$, you can factor $k$ and make some cycles whose $operatorname {LCM}$ is $k$. In your example of $35$ we note that $35=5cdot 7$, so if you make a $5-$cycle and a $7-$cycle you will have an element of order $35$. As $5+7=12$ you have enough room to do this in $S_{12}$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thanks I get it now. How can I find the maximum order possible?
    $endgroup$
    – vesii
    Jan 1 at 15:15






  • 1




    $begingroup$
    $35$ is the best you can do with just two cycles, but once $n$ gets large enough you can do better with three separate cycles. $12$ is large enough that three cycles gives a higher LCM. Values of the maximum are given in oeis.org/A000793
    $endgroup$
    – Ross Millikan
    Jan 1 at 15:26





















0












$begingroup$

Hint: $35 = 5 cdot 7$ and $5+7=12$.






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    2 Answers
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    2 Answers
    2






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    4












    $begingroup$

    If you want an element of order $k$, you can factor $k$ and make some cycles whose $operatorname {LCM}$ is $k$. In your example of $35$ we note that $35=5cdot 7$, so if you make a $5-$cycle and a $7-$cycle you will have an element of order $35$. As $5+7=12$ you have enough room to do this in $S_{12}$






    share|cite|improve this answer









    $endgroup$













    • $begingroup$
      Thanks I get it now. How can I find the maximum order possible?
      $endgroup$
      – vesii
      Jan 1 at 15:15






    • 1




      $begingroup$
      $35$ is the best you can do with just two cycles, but once $n$ gets large enough you can do better with three separate cycles. $12$ is large enough that three cycles gives a higher LCM. Values of the maximum are given in oeis.org/A000793
      $endgroup$
      – Ross Millikan
      Jan 1 at 15:26


















    4












    $begingroup$

    If you want an element of order $k$, you can factor $k$ and make some cycles whose $operatorname {LCM}$ is $k$. In your example of $35$ we note that $35=5cdot 7$, so if you make a $5-$cycle and a $7-$cycle you will have an element of order $35$. As $5+7=12$ you have enough room to do this in $S_{12}$






    share|cite|improve this answer









    $endgroup$













    • $begingroup$
      Thanks I get it now. How can I find the maximum order possible?
      $endgroup$
      – vesii
      Jan 1 at 15:15






    • 1




      $begingroup$
      $35$ is the best you can do with just two cycles, but once $n$ gets large enough you can do better with three separate cycles. $12$ is large enough that three cycles gives a higher LCM. Values of the maximum are given in oeis.org/A000793
      $endgroup$
      – Ross Millikan
      Jan 1 at 15:26
















    4












    4








    4





    $begingroup$

    If you want an element of order $k$, you can factor $k$ and make some cycles whose $operatorname {LCM}$ is $k$. In your example of $35$ we note that $35=5cdot 7$, so if you make a $5-$cycle and a $7-$cycle you will have an element of order $35$. As $5+7=12$ you have enough room to do this in $S_{12}$






    share|cite|improve this answer









    $endgroup$



    If you want an element of order $k$, you can factor $k$ and make some cycles whose $operatorname {LCM}$ is $k$. In your example of $35$ we note that $35=5cdot 7$, so if you make a $5-$cycle and a $7-$cycle you will have an element of order $35$. As $5+7=12$ you have enough room to do this in $S_{12}$







    share|cite|improve this answer












    share|cite|improve this answer



    share|cite|improve this answer










    answered Jan 1 at 15:04









    Ross MillikanRoss Millikan

    293k23197371




    293k23197371












    • $begingroup$
      Thanks I get it now. How can I find the maximum order possible?
      $endgroup$
      – vesii
      Jan 1 at 15:15






    • 1




      $begingroup$
      $35$ is the best you can do with just two cycles, but once $n$ gets large enough you can do better with three separate cycles. $12$ is large enough that three cycles gives a higher LCM. Values of the maximum are given in oeis.org/A000793
      $endgroup$
      – Ross Millikan
      Jan 1 at 15:26




















    • $begingroup$
      Thanks I get it now. How can I find the maximum order possible?
      $endgroup$
      – vesii
      Jan 1 at 15:15






    • 1




      $begingroup$
      $35$ is the best you can do with just two cycles, but once $n$ gets large enough you can do better with three separate cycles. $12$ is large enough that three cycles gives a higher LCM. Values of the maximum are given in oeis.org/A000793
      $endgroup$
      – Ross Millikan
      Jan 1 at 15:26


















    $begingroup$
    Thanks I get it now. How can I find the maximum order possible?
    $endgroup$
    – vesii
    Jan 1 at 15:15




    $begingroup$
    Thanks I get it now. How can I find the maximum order possible?
    $endgroup$
    – vesii
    Jan 1 at 15:15




    1




    1




    $begingroup$
    $35$ is the best you can do with just two cycles, but once $n$ gets large enough you can do better with three separate cycles. $12$ is large enough that three cycles gives a higher LCM. Values of the maximum are given in oeis.org/A000793
    $endgroup$
    – Ross Millikan
    Jan 1 at 15:26






    $begingroup$
    $35$ is the best you can do with just two cycles, but once $n$ gets large enough you can do better with three separate cycles. $12$ is large enough that three cycles gives a higher LCM. Values of the maximum are given in oeis.org/A000793
    $endgroup$
    – Ross Millikan
    Jan 1 at 15:26













    0












    $begingroup$

    Hint: $35 = 5 cdot 7$ and $5+7=12$.






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      Hint: $35 = 5 cdot 7$ and $5+7=12$.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        Hint: $35 = 5 cdot 7$ and $5+7=12$.






        share|cite|improve this answer









        $endgroup$



        Hint: $35 = 5 cdot 7$ and $5+7=12$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 1 at 15:03









        lhflhf

        163k10168388




        163k10168388






























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