Dimension of a vector space $W={f in V; f circ pi = f}$












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Let $N={1,2,3,4,5,6,7}$ and $pi$ a permutation $pi: N rightarrow N$.$$pi=(14)(235)(67)$$ Let $V$ be the vector space of all functions $N rightarrow mathbb{R}$. Let $W$ be the following set, $$W={f in V; f circ pi = f}$$ What is the dimension of $W$?










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  • $begingroup$
    What have you tried and where did you get stuck? This is just a problem statement, which is generally not received well.
    $endgroup$
    – Servaes
    Jan 21 at 21:23










  • $begingroup$
    Also, how can $pi$ permute $7$ when $7notin N$?
    $endgroup$
    – Servaes
    Jan 21 at 21:23










  • $begingroup$
    Please add at least a modicum of context to tell Readers where your interest or difficulty in this problem lies. Are you able to make any progress (such as an upper or lower bound on the dimension)?
    $endgroup$
    – hardmath
    Jan 22 at 3:53
















0












$begingroup$


Let $N={1,2,3,4,5,6,7}$ and $pi$ a permutation $pi: N rightarrow N$.$$pi=(14)(235)(67)$$ Let $V$ be the vector space of all functions $N rightarrow mathbb{R}$. Let $W$ be the following set, $$W={f in V; f circ pi = f}$$ What is the dimension of $W$?










share|cite|improve this question











$endgroup$












  • $begingroup$
    What have you tried and where did you get stuck? This is just a problem statement, which is generally not received well.
    $endgroup$
    – Servaes
    Jan 21 at 21:23










  • $begingroup$
    Also, how can $pi$ permute $7$ when $7notin N$?
    $endgroup$
    – Servaes
    Jan 21 at 21:23










  • $begingroup$
    Please add at least a modicum of context to tell Readers where your interest or difficulty in this problem lies. Are you able to make any progress (such as an upper or lower bound on the dimension)?
    $endgroup$
    – hardmath
    Jan 22 at 3:53














0












0








0





$begingroup$


Let $N={1,2,3,4,5,6,7}$ and $pi$ a permutation $pi: N rightarrow N$.$$pi=(14)(235)(67)$$ Let $V$ be the vector space of all functions $N rightarrow mathbb{R}$. Let $W$ be the following set, $$W={f in V; f circ pi = f}$$ What is the dimension of $W$?










share|cite|improve this question











$endgroup$




Let $N={1,2,3,4,5,6,7}$ and $pi$ a permutation $pi: N rightarrow N$.$$pi=(14)(235)(67)$$ Let $V$ be the vector space of all functions $N rightarrow mathbb{R}$. Let $W$ be the following set, $$W={f in V; f circ pi = f}$$ What is the dimension of $W$?







linear-algebra vector-spaces






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edited Jan 21 at 21:24







nene123

















asked Jan 21 at 21:22









nene123nene123

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284












  • $begingroup$
    What have you tried and where did you get stuck? This is just a problem statement, which is generally not received well.
    $endgroup$
    – Servaes
    Jan 21 at 21:23










  • $begingroup$
    Also, how can $pi$ permute $7$ when $7notin N$?
    $endgroup$
    – Servaes
    Jan 21 at 21:23










  • $begingroup$
    Please add at least a modicum of context to tell Readers where your interest or difficulty in this problem lies. Are you able to make any progress (such as an upper or lower bound on the dimension)?
    $endgroup$
    – hardmath
    Jan 22 at 3:53


















  • $begingroup$
    What have you tried and where did you get stuck? This is just a problem statement, which is generally not received well.
    $endgroup$
    – Servaes
    Jan 21 at 21:23










  • $begingroup$
    Also, how can $pi$ permute $7$ when $7notin N$?
    $endgroup$
    – Servaes
    Jan 21 at 21:23










  • $begingroup$
    Please add at least a modicum of context to tell Readers where your interest or difficulty in this problem lies. Are you able to make any progress (such as an upper or lower bound on the dimension)?
    $endgroup$
    – hardmath
    Jan 22 at 3:53
















$begingroup$
What have you tried and where did you get stuck? This is just a problem statement, which is generally not received well.
$endgroup$
– Servaes
Jan 21 at 21:23




$begingroup$
What have you tried and where did you get stuck? This is just a problem statement, which is generally not received well.
$endgroup$
– Servaes
Jan 21 at 21:23












$begingroup$
Also, how can $pi$ permute $7$ when $7notin N$?
$endgroup$
– Servaes
Jan 21 at 21:23




$begingroup$
Also, how can $pi$ permute $7$ when $7notin N$?
$endgroup$
– Servaes
Jan 21 at 21:23












$begingroup$
Please add at least a modicum of context to tell Readers where your interest or difficulty in this problem lies. Are you able to make any progress (such as an upper or lower bound on the dimension)?
$endgroup$
– hardmath
Jan 22 at 3:53




$begingroup$
Please add at least a modicum of context to tell Readers where your interest or difficulty in this problem lies. Are you able to make any progress (such as an upper or lower bound on the dimension)?
$endgroup$
– hardmath
Jan 22 at 3:53










2 Answers
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Hint
Let $f in W$, then $f(pi(1))=f(1) implies f(4)=f(1)$. Likewise $f(2)=f(3)=f(5)$ and $f(6)=f(7)$. So there is only so much freedom to choose the values for $f$.......???






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    0












    $begingroup$

    We have
    $$f(1)=f(4)$$
    $$f(2)=f(3)=f(5)$$
    $$f(6)=f(7)$$
    The subspace satisfying these equations has dimension $3$.






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      2 Answers
      2






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      2 Answers
      2






      active

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      active

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      0












      $begingroup$

      Hint
      Let $f in W$, then $f(pi(1))=f(1) implies f(4)=f(1)$. Likewise $f(2)=f(3)=f(5)$ and $f(6)=f(7)$. So there is only so much freedom to choose the values for $f$.......???






      share|cite|improve this answer









      $endgroup$


















        0












        $begingroup$

        Hint
        Let $f in W$, then $f(pi(1))=f(1) implies f(4)=f(1)$. Likewise $f(2)=f(3)=f(5)$ and $f(6)=f(7)$. So there is only so much freedom to choose the values for $f$.......???






        share|cite|improve this answer









        $endgroup$
















          0












          0








          0





          $begingroup$

          Hint
          Let $f in W$, then $f(pi(1))=f(1) implies f(4)=f(1)$. Likewise $f(2)=f(3)=f(5)$ and $f(6)=f(7)$. So there is only so much freedom to choose the values for $f$.......???






          share|cite|improve this answer









          $endgroup$



          Hint
          Let $f in W$, then $f(pi(1))=f(1) implies f(4)=f(1)$. Likewise $f(2)=f(3)=f(5)$ and $f(6)=f(7)$. So there is only so much freedom to choose the values for $f$.......???







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 21 at 21:27









          Anurag AAnurag A

          26.3k12251




          26.3k12251























              0












              $begingroup$

              We have
              $$f(1)=f(4)$$
              $$f(2)=f(3)=f(5)$$
              $$f(6)=f(7)$$
              The subspace satisfying these equations has dimension $3$.






              share|cite|improve this answer









              $endgroup$


















                0












                $begingroup$

                We have
                $$f(1)=f(4)$$
                $$f(2)=f(3)=f(5)$$
                $$f(6)=f(7)$$
                The subspace satisfying these equations has dimension $3$.






                share|cite|improve this answer









                $endgroup$
















                  0












                  0








                  0





                  $begingroup$

                  We have
                  $$f(1)=f(4)$$
                  $$f(2)=f(3)=f(5)$$
                  $$f(6)=f(7)$$
                  The subspace satisfying these equations has dimension $3$.






                  share|cite|improve this answer









                  $endgroup$



                  We have
                  $$f(1)=f(4)$$
                  $$f(2)=f(3)=f(5)$$
                  $$f(6)=f(7)$$
                  The subspace satisfying these equations has dimension $3$.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Jan 21 at 21:29









                  Matt SamuelMatt Samuel

                  38.8k63769




                  38.8k63769






























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