Yet another problem of terminology about permutations












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I am looking for notations and ways to formalize applications/functions involving permutations.



Let a sequence of integers $1$, $2$, ... $n$. How to formalize, mathematically, a permutation that consists to randomly permute the $n-1$ first integers, letting unchanged the last one, $n$.



Thank you.










share|cite|improve this question









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    0












    $begingroup$


    I am looking for notations and ways to formalize applications/functions involving permutations.



    Let a sequence of integers $1$, $2$, ... $n$. How to formalize, mathematically, a permutation that consists to randomly permute the $n-1$ first integers, letting unchanged the last one, $n$.



    Thank you.










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      I am looking for notations and ways to formalize applications/functions involving permutations.



      Let a sequence of integers $1$, $2$, ... $n$. How to formalize, mathematically, a permutation that consists to randomly permute the $n-1$ first integers, letting unchanged the last one, $n$.



      Thank you.










      share|cite|improve this question









      $endgroup$




      I am looking for notations and ways to formalize applications/functions involving permutations.



      Let a sequence of integers $1$, $2$, ... $n$. How to formalize, mathematically, a permutation that consists to randomly permute the $n-1$ first integers, letting unchanged the last one, $n$.



      Thank you.







      probability probability-theory permutations






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      share|cite|improve this question











      share|cite|improve this question




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      asked Jan 13 at 20:15









      Adam54Adam54

      895




      895






















          1 Answer
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          $begingroup$

          This (PDF) does an excellent job of going over the various notations for permutations.



          In this case, you've already formalised it. However, what you're doing is choosing a random element of $S_{n-1}$, taking the (first) natural inclusion of $S_{n-1}$ in $S_n$, and taking the image of your random element under that inclusion (equivalently, you're choosing a random element of the stabiliser $mathrm{Stab}_{S_n}(n)$ of $n$ inside $S_n$).






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you for your answer and the link. So, the searched term is "stabiliser"? I have not found the term in the linked pdf.
            $endgroup$
            – Adam54
            Jan 13 at 20:24










          • $begingroup$
            The linked PDF doesn't take the stabiliser approach: it goes for the other one instead. Specifically: there's a map from $S_{n-1}$ to $S_n$ given by taken every permutation in $S_{n-1}$ and extending it to a permutation of ${1,ldots,n}$ by just leaving $n$ unchanged. You're simply selecting an element of $S_{n-1}$, then passing it through that map. Of course, the image of that map is isomorphic to $S_{n-1}$, so for most purposes, you might as well just stick to $S_{n-1}$.
            $endgroup$
            – user3482749
            Jan 13 at 23:10











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          1 Answer
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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1












          $begingroup$

          This (PDF) does an excellent job of going over the various notations for permutations.



          In this case, you've already formalised it. However, what you're doing is choosing a random element of $S_{n-1}$, taking the (first) natural inclusion of $S_{n-1}$ in $S_n$, and taking the image of your random element under that inclusion (equivalently, you're choosing a random element of the stabiliser $mathrm{Stab}_{S_n}(n)$ of $n$ inside $S_n$).






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you for your answer and the link. So, the searched term is "stabiliser"? I have not found the term in the linked pdf.
            $endgroup$
            – Adam54
            Jan 13 at 20:24










          • $begingroup$
            The linked PDF doesn't take the stabiliser approach: it goes for the other one instead. Specifically: there's a map from $S_{n-1}$ to $S_n$ given by taken every permutation in $S_{n-1}$ and extending it to a permutation of ${1,ldots,n}$ by just leaving $n$ unchanged. You're simply selecting an element of $S_{n-1}$, then passing it through that map. Of course, the image of that map is isomorphic to $S_{n-1}$, so for most purposes, you might as well just stick to $S_{n-1}$.
            $endgroup$
            – user3482749
            Jan 13 at 23:10
















          1












          $begingroup$

          This (PDF) does an excellent job of going over the various notations for permutations.



          In this case, you've already formalised it. However, what you're doing is choosing a random element of $S_{n-1}$, taking the (first) natural inclusion of $S_{n-1}$ in $S_n$, and taking the image of your random element under that inclusion (equivalently, you're choosing a random element of the stabiliser $mathrm{Stab}_{S_n}(n)$ of $n$ inside $S_n$).






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you for your answer and the link. So, the searched term is "stabiliser"? I have not found the term in the linked pdf.
            $endgroup$
            – Adam54
            Jan 13 at 20:24










          • $begingroup$
            The linked PDF doesn't take the stabiliser approach: it goes for the other one instead. Specifically: there's a map from $S_{n-1}$ to $S_n$ given by taken every permutation in $S_{n-1}$ and extending it to a permutation of ${1,ldots,n}$ by just leaving $n$ unchanged. You're simply selecting an element of $S_{n-1}$, then passing it through that map. Of course, the image of that map is isomorphic to $S_{n-1}$, so for most purposes, you might as well just stick to $S_{n-1}$.
            $endgroup$
            – user3482749
            Jan 13 at 23:10














          1












          1








          1





          $begingroup$

          This (PDF) does an excellent job of going over the various notations for permutations.



          In this case, you've already formalised it. However, what you're doing is choosing a random element of $S_{n-1}$, taking the (first) natural inclusion of $S_{n-1}$ in $S_n$, and taking the image of your random element under that inclusion (equivalently, you're choosing a random element of the stabiliser $mathrm{Stab}_{S_n}(n)$ of $n$ inside $S_n$).






          share|cite|improve this answer









          $endgroup$



          This (PDF) does an excellent job of going over the various notations for permutations.



          In this case, you've already formalised it. However, what you're doing is choosing a random element of $S_{n-1}$, taking the (first) natural inclusion of $S_{n-1}$ in $S_n$, and taking the image of your random element under that inclusion (equivalently, you're choosing a random element of the stabiliser $mathrm{Stab}_{S_n}(n)$ of $n$ inside $S_n$).







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 13 at 20:19









          user3482749user3482749

          4,266919




          4,266919












          • $begingroup$
            Thank you for your answer and the link. So, the searched term is "stabiliser"? I have not found the term in the linked pdf.
            $endgroup$
            – Adam54
            Jan 13 at 20:24










          • $begingroup$
            The linked PDF doesn't take the stabiliser approach: it goes for the other one instead. Specifically: there's a map from $S_{n-1}$ to $S_n$ given by taken every permutation in $S_{n-1}$ and extending it to a permutation of ${1,ldots,n}$ by just leaving $n$ unchanged. You're simply selecting an element of $S_{n-1}$, then passing it through that map. Of course, the image of that map is isomorphic to $S_{n-1}$, so for most purposes, you might as well just stick to $S_{n-1}$.
            $endgroup$
            – user3482749
            Jan 13 at 23:10


















          • $begingroup$
            Thank you for your answer and the link. So, the searched term is "stabiliser"? I have not found the term in the linked pdf.
            $endgroup$
            – Adam54
            Jan 13 at 20:24










          • $begingroup$
            The linked PDF doesn't take the stabiliser approach: it goes for the other one instead. Specifically: there's a map from $S_{n-1}$ to $S_n$ given by taken every permutation in $S_{n-1}$ and extending it to a permutation of ${1,ldots,n}$ by just leaving $n$ unchanged. You're simply selecting an element of $S_{n-1}$, then passing it through that map. Of course, the image of that map is isomorphic to $S_{n-1}$, so for most purposes, you might as well just stick to $S_{n-1}$.
            $endgroup$
            – user3482749
            Jan 13 at 23:10
















          $begingroup$
          Thank you for your answer and the link. So, the searched term is "stabiliser"? I have not found the term in the linked pdf.
          $endgroup$
          – Adam54
          Jan 13 at 20:24




          $begingroup$
          Thank you for your answer and the link. So, the searched term is "stabiliser"? I have not found the term in the linked pdf.
          $endgroup$
          – Adam54
          Jan 13 at 20:24












          $begingroup$
          The linked PDF doesn't take the stabiliser approach: it goes for the other one instead. Specifically: there's a map from $S_{n-1}$ to $S_n$ given by taken every permutation in $S_{n-1}$ and extending it to a permutation of ${1,ldots,n}$ by just leaving $n$ unchanged. You're simply selecting an element of $S_{n-1}$, then passing it through that map. Of course, the image of that map is isomorphic to $S_{n-1}$, so for most purposes, you might as well just stick to $S_{n-1}$.
          $endgroup$
          – user3482749
          Jan 13 at 23:10




          $begingroup$
          The linked PDF doesn't take the stabiliser approach: it goes for the other one instead. Specifically: there's a map from $S_{n-1}$ to $S_n$ given by taken every permutation in $S_{n-1}$ and extending it to a permutation of ${1,ldots,n}$ by just leaving $n$ unchanged. You're simply selecting an element of $S_{n-1}$, then passing it through that map. Of course, the image of that map is isomorphic to $S_{n-1}$, so for most purposes, you might as well just stick to $S_{n-1}$.
          $endgroup$
          – user3482749
          Jan 13 at 23:10


















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