Centre of non-abelian group of order $p^3$, where $p$ is prime












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If $p$ is a prime number and $G$ is a non-abelian group of order $p^3$, then what can we say about the number of elements in the centre of the group $G$, i.e. $Z(G)$?










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    $begingroup$


    If $p$ is a prime number and $G$ is a non-abelian group of order $p^3$, then what can we say about the number of elements in the centre of the group $G$, i.e. $Z(G)$?










    share|cite|improve this question











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      0








      0





      $begingroup$


      If $p$ is a prime number and $G$ is a non-abelian group of order $p^3$, then what can we say about the number of elements in the centre of the group $G$, i.e. $Z(G)$?










      share|cite|improve this question











      $endgroup$




      If $p$ is a prime number and $G$ is a non-abelian group of order $p^3$, then what can we say about the number of elements in the centre of the group $G$, i.e. $Z(G)$?







      abstract-algebra group-theory






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      edited Nov 25 '18 at 13:49









      the_fox

      2,58711533




      2,58711533










      asked Nov 25 '18 at 13:16









      kapil pundirkapil pundir

      574




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          1 Answer
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          $begingroup$

          Hint:By class equation, it can be shown that $Z(G)$ is non-trivial. Now if $O(Z(G)) =p^2 $,we will have order of $frac{G}{Z(G)}=p $,which will imply $frac{G}{Z(G)}$ is cyclic. But that will imply $G$ is abelian(Verify),leading to a contradiction. Then the only other possibility is $p$,since it is already given that $G$ is non-abelian.






          share|cite|improve this answer









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          • $begingroup$
            Do we have some method other than 'class equation' to show that Z(G) is non trivial?
            $endgroup$
            – kapil pundir
            Nov 25 '18 at 14:52










          • $begingroup$
            I'm sure there are, but it's the easiest way. To see that counting is likely to be involved in some essential way, note that there are infinite p-groups with trivial center. But all finite p-groups have non-trivial center (by the class equation argument).
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:15








          • 1




            $begingroup$
            Note that the class equation argument is elementary. All conjugacy classes have order a power of p, and the group is divisible by p. Thus, if one conjugacy class has size 1, at least p-1 more must also be size 1 so that the sum is divisible by p.
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:18













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          $begingroup$

          Hint:By class equation, it can be shown that $Z(G)$ is non-trivial. Now if $O(Z(G)) =p^2 $,we will have order of $frac{G}{Z(G)}=p $,which will imply $frac{G}{Z(G)}$ is cyclic. But that will imply $G$ is abelian(Verify),leading to a contradiction. Then the only other possibility is $p$,since it is already given that $G$ is non-abelian.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Do we have some method other than 'class equation' to show that Z(G) is non trivial?
            $endgroup$
            – kapil pundir
            Nov 25 '18 at 14:52










          • $begingroup$
            I'm sure there are, but it's the easiest way. To see that counting is likely to be involved in some essential way, note that there are infinite p-groups with trivial center. But all finite p-groups have non-trivial center (by the class equation argument).
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:15








          • 1




            $begingroup$
            Note that the class equation argument is elementary. All conjugacy classes have order a power of p, and the group is divisible by p. Thus, if one conjugacy class has size 1, at least p-1 more must also be size 1 so that the sum is divisible by p.
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:18


















          3












          $begingroup$

          Hint:By class equation, it can be shown that $Z(G)$ is non-trivial. Now if $O(Z(G)) =p^2 $,we will have order of $frac{G}{Z(G)}=p $,which will imply $frac{G}{Z(G)}$ is cyclic. But that will imply $G$ is abelian(Verify),leading to a contradiction. Then the only other possibility is $p$,since it is already given that $G$ is non-abelian.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Do we have some method other than 'class equation' to show that Z(G) is non trivial?
            $endgroup$
            – kapil pundir
            Nov 25 '18 at 14:52










          • $begingroup$
            I'm sure there are, but it's the easiest way. To see that counting is likely to be involved in some essential way, note that there are infinite p-groups with trivial center. But all finite p-groups have non-trivial center (by the class equation argument).
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:15








          • 1




            $begingroup$
            Note that the class equation argument is elementary. All conjugacy classes have order a power of p, and the group is divisible by p. Thus, if one conjugacy class has size 1, at least p-1 more must also be size 1 so that the sum is divisible by p.
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:18
















          3












          3








          3





          $begingroup$

          Hint:By class equation, it can be shown that $Z(G)$ is non-trivial. Now if $O(Z(G)) =p^2 $,we will have order of $frac{G}{Z(G)}=p $,which will imply $frac{G}{Z(G)}$ is cyclic. But that will imply $G$ is abelian(Verify),leading to a contradiction. Then the only other possibility is $p$,since it is already given that $G$ is non-abelian.






          share|cite|improve this answer









          $endgroup$



          Hint:By class equation, it can be shown that $Z(G)$ is non-trivial. Now if $O(Z(G)) =p^2 $,we will have order of $frac{G}{Z(G)}=p $,which will imply $frac{G}{Z(G)}$ is cyclic. But that will imply $G$ is abelian(Verify),leading to a contradiction. Then the only other possibility is $p$,since it is already given that $G$ is non-abelian.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Nov 25 '18 at 13:29









          Thomas ShelbyThomas Shelby

          2,250220




          2,250220












          • $begingroup$
            Do we have some method other than 'class equation' to show that Z(G) is non trivial?
            $endgroup$
            – kapil pundir
            Nov 25 '18 at 14:52










          • $begingroup$
            I'm sure there are, but it's the easiest way. To see that counting is likely to be involved in some essential way, note that there are infinite p-groups with trivial center. But all finite p-groups have non-trivial center (by the class equation argument).
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:15








          • 1




            $begingroup$
            Note that the class equation argument is elementary. All conjugacy classes have order a power of p, and the group is divisible by p. Thus, if one conjugacy class has size 1, at least p-1 more must also be size 1 so that the sum is divisible by p.
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:18




















          • $begingroup$
            Do we have some method other than 'class equation' to show that Z(G) is non trivial?
            $endgroup$
            – kapil pundir
            Nov 25 '18 at 14:52










          • $begingroup$
            I'm sure there are, but it's the easiest way. To see that counting is likely to be involved in some essential way, note that there are infinite p-groups with trivial center. But all finite p-groups have non-trivial center (by the class equation argument).
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:15








          • 1




            $begingroup$
            Note that the class equation argument is elementary. All conjugacy classes have order a power of p, and the group is divisible by p. Thus, if one conjugacy class has size 1, at least p-1 more must also be size 1 so that the sum is divisible by p.
            $endgroup$
            – C Monsour
            Nov 25 '18 at 15:18


















          $begingroup$
          Do we have some method other than 'class equation' to show that Z(G) is non trivial?
          $endgroup$
          – kapil pundir
          Nov 25 '18 at 14:52




          $begingroup$
          Do we have some method other than 'class equation' to show that Z(G) is non trivial?
          $endgroup$
          – kapil pundir
          Nov 25 '18 at 14:52












          $begingroup$
          I'm sure there are, but it's the easiest way. To see that counting is likely to be involved in some essential way, note that there are infinite p-groups with trivial center. But all finite p-groups have non-trivial center (by the class equation argument).
          $endgroup$
          – C Monsour
          Nov 25 '18 at 15:15






          $begingroup$
          I'm sure there are, but it's the easiest way. To see that counting is likely to be involved in some essential way, note that there are infinite p-groups with trivial center. But all finite p-groups have non-trivial center (by the class equation argument).
          $endgroup$
          – C Monsour
          Nov 25 '18 at 15:15






          1




          1




          $begingroup$
          Note that the class equation argument is elementary. All conjugacy classes have order a power of p, and the group is divisible by p. Thus, if one conjugacy class has size 1, at least p-1 more must also be size 1 so that the sum is divisible by p.
          $endgroup$
          – C Monsour
          Nov 25 '18 at 15:18






          $begingroup$
          Note that the class equation argument is elementary. All conjugacy classes have order a power of p, and the group is divisible by p. Thus, if one conjugacy class has size 1, at least p-1 more must also be size 1 so that the sum is divisible by p.
          $endgroup$
          – C Monsour
          Nov 25 '18 at 15:18




















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