What is the relation between $lVert{Hp}rVert^2$ and $lVert{H}rVert$ when $Hpne0$ and $lVert{p}rVert = 1$?












0












$begingroup$


What is the relation between $lVert{Hp}rVert^2$ and $lVert{H}rVert$ when $Hpne0$ and $lVert{p}rVert = 1$?



Note that $H$ and $p$ are sampled value of Gaussian distributed random variables, in which $H$ is a vector with a size of $1$ by $N$ and $p$ is a vector with a size of $N$ by $1$?



I think $$lVert{Hp}rVert^2 = lVert{H}rVert.$$
However, I failed to prove the above equation.
Is my thought wrong?
Thanks for reading my question.










share|cite|improve this question









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    0












    $begingroup$


    What is the relation between $lVert{Hp}rVert^2$ and $lVert{H}rVert$ when $Hpne0$ and $lVert{p}rVert = 1$?



    Note that $H$ and $p$ are sampled value of Gaussian distributed random variables, in which $H$ is a vector with a size of $1$ by $N$ and $p$ is a vector with a size of $N$ by $1$?



    I think $$lVert{Hp}rVert^2 = lVert{H}rVert.$$
    However, I failed to prove the above equation.
    Is my thought wrong?
    Thanks for reading my question.










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      What is the relation between $lVert{Hp}rVert^2$ and $lVert{H}rVert$ when $Hpne0$ and $lVert{p}rVert = 1$?



      Note that $H$ and $p$ are sampled value of Gaussian distributed random variables, in which $H$ is a vector with a size of $1$ by $N$ and $p$ is a vector with a size of $N$ by $1$?



      I think $$lVert{Hp}rVert^2 = lVert{H}rVert.$$
      However, I failed to prove the above equation.
      Is my thought wrong?
      Thanks for reading my question.










      share|cite|improve this question









      $endgroup$




      What is the relation between $lVert{Hp}rVert^2$ and $lVert{H}rVert$ when $Hpne0$ and $lVert{p}rVert = 1$?



      Note that $H$ and $p$ are sampled value of Gaussian distributed random variables, in which $H$ is a vector with a size of $1$ by $N$ and $p$ is a vector with a size of $N$ by $1$?



      I think $$lVert{Hp}rVert^2 = lVert{H}rVert.$$
      However, I failed to prove the above equation.
      Is my thought wrong?
      Thanks for reading my question.







      vectors






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 27 at 14:28









      Danny_KimDanny_Kim

      1,3911624




      1,3911624






















          1 Answer
          1






          active

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          0












          $begingroup$

          All you can state is
          $$|Hp|^2 le |H|^2$$
          Can you prove this one?






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Actually, I tried many times using MATLAB program. I could observe that the value of RHS is much larger than that of LHS.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:46










          • $begingroup$
            Well, by compactness of the unit sphere, there exists a unit vector $p$ such that $|Hp|=|H|$..
            $endgroup$
            – Berci
            Jan 27 at 14:52










          • $begingroup$
            However, to prove $lVert HprVert^2 le lVert HrVert^2$, do we have to prove that there do not exist $p$ such that $lVert HprVert^2 ge lVert HrVert^2$? Intuitively, each element of $p$ must be less than $1$, so each element of $Hp$ MAY be less than or equal to that of $H$. Is it enough to prove the above equation? I am not sure that it is enough.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:55













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          1 Answer
          1






          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          0












          $begingroup$

          All you can state is
          $$|Hp|^2 le |H|^2$$
          Can you prove this one?






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Actually, I tried many times using MATLAB program. I could observe that the value of RHS is much larger than that of LHS.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:46










          • $begingroup$
            Well, by compactness of the unit sphere, there exists a unit vector $p$ such that $|Hp|=|H|$..
            $endgroup$
            – Berci
            Jan 27 at 14:52










          • $begingroup$
            However, to prove $lVert HprVert^2 le lVert HrVert^2$, do we have to prove that there do not exist $p$ such that $lVert HprVert^2 ge lVert HrVert^2$? Intuitively, each element of $p$ must be less than $1$, so each element of $Hp$ MAY be less than or equal to that of $H$. Is it enough to prove the above equation? I am not sure that it is enough.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:55


















          0












          $begingroup$

          All you can state is
          $$|Hp|^2 le |H|^2$$
          Can you prove this one?






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Actually, I tried many times using MATLAB program. I could observe that the value of RHS is much larger than that of LHS.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:46










          • $begingroup$
            Well, by compactness of the unit sphere, there exists a unit vector $p$ such that $|Hp|=|H|$..
            $endgroup$
            – Berci
            Jan 27 at 14:52










          • $begingroup$
            However, to prove $lVert HprVert^2 le lVert HrVert^2$, do we have to prove that there do not exist $p$ such that $lVert HprVert^2 ge lVert HrVert^2$? Intuitively, each element of $p$ must be less than $1$, so each element of $Hp$ MAY be less than or equal to that of $H$. Is it enough to prove the above equation? I am not sure that it is enough.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:55
















          0












          0








          0





          $begingroup$

          All you can state is
          $$|Hp|^2 le |H|^2$$
          Can you prove this one?






          share|cite|improve this answer









          $endgroup$



          All you can state is
          $$|Hp|^2 le |H|^2$$
          Can you prove this one?







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 27 at 14:40









          BerciBerci

          61.7k23674




          61.7k23674












          • $begingroup$
            Actually, I tried many times using MATLAB program. I could observe that the value of RHS is much larger than that of LHS.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:46










          • $begingroup$
            Well, by compactness of the unit sphere, there exists a unit vector $p$ such that $|Hp|=|H|$..
            $endgroup$
            – Berci
            Jan 27 at 14:52










          • $begingroup$
            However, to prove $lVert HprVert^2 le lVert HrVert^2$, do we have to prove that there do not exist $p$ such that $lVert HprVert^2 ge lVert HrVert^2$? Intuitively, each element of $p$ must be less than $1$, so each element of $Hp$ MAY be less than or equal to that of $H$. Is it enough to prove the above equation? I am not sure that it is enough.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:55




















          • $begingroup$
            Actually, I tried many times using MATLAB program. I could observe that the value of RHS is much larger than that of LHS.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:46










          • $begingroup$
            Well, by compactness of the unit sphere, there exists a unit vector $p$ such that $|Hp|=|H|$..
            $endgroup$
            – Berci
            Jan 27 at 14:52










          • $begingroup$
            However, to prove $lVert HprVert^2 le lVert HrVert^2$, do we have to prove that there do not exist $p$ such that $lVert HprVert^2 ge lVert HrVert^2$? Intuitively, each element of $p$ must be less than $1$, so each element of $Hp$ MAY be less than or equal to that of $H$. Is it enough to prove the above equation? I am not sure that it is enough.
            $endgroup$
            – Danny_Kim
            Jan 27 at 14:55


















          $begingroup$
          Actually, I tried many times using MATLAB program. I could observe that the value of RHS is much larger than that of LHS.
          $endgroup$
          – Danny_Kim
          Jan 27 at 14:46




          $begingroup$
          Actually, I tried many times using MATLAB program. I could observe that the value of RHS is much larger than that of LHS.
          $endgroup$
          – Danny_Kim
          Jan 27 at 14:46












          $begingroup$
          Well, by compactness of the unit sphere, there exists a unit vector $p$ such that $|Hp|=|H|$..
          $endgroup$
          – Berci
          Jan 27 at 14:52




          $begingroup$
          Well, by compactness of the unit sphere, there exists a unit vector $p$ such that $|Hp|=|H|$..
          $endgroup$
          – Berci
          Jan 27 at 14:52












          $begingroup$
          However, to prove $lVert HprVert^2 le lVert HrVert^2$, do we have to prove that there do not exist $p$ such that $lVert HprVert^2 ge lVert HrVert^2$? Intuitively, each element of $p$ must be less than $1$, so each element of $Hp$ MAY be less than or equal to that of $H$. Is it enough to prove the above equation? I am not sure that it is enough.
          $endgroup$
          – Danny_Kim
          Jan 27 at 14:55






          $begingroup$
          However, to prove $lVert HprVert^2 le lVert HrVert^2$, do we have to prove that there do not exist $p$ such that $lVert HprVert^2 ge lVert HrVert^2$? Intuitively, each element of $p$ must be less than $1$, so each element of $Hp$ MAY be less than or equal to that of $H$. Is it enough to prove the above equation? I am not sure that it is enough.
          $endgroup$
          – Danny_Kim
          Jan 27 at 14:55




















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