Matrices and Manifolds












0












$begingroup$


I have a huge problem solving this question. Does anybody have literature on this or maybe a solution?



Let
$
M:={xin mathbb{R}^n : x^{⊤} A x = r} subset mathbb{R}^n
$

for $r>0$ and $A$ being a symmetric, positive semidefinite Matrix $Ain mathbb{R}^{n times n}$



Is $M$ a $C^l$-Submanifold of $mathbb{R}^n$. If so, of which Dimension?










share|cite|improve this question











$endgroup$

















    0












    $begingroup$


    I have a huge problem solving this question. Does anybody have literature on this or maybe a solution?



    Let
    $
    M:={xin mathbb{R}^n : x^{⊤} A x = r} subset mathbb{R}^n
    $

    for $r>0$ and $A$ being a symmetric, positive semidefinite Matrix $Ain mathbb{R}^{n times n}$



    Is $M$ a $C^l$-Submanifold of $mathbb{R}^n$. If so, of which Dimension?










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      I have a huge problem solving this question. Does anybody have literature on this or maybe a solution?



      Let
      $
      M:={xin mathbb{R}^n : x^{⊤} A x = r} subset mathbb{R}^n
      $

      for $r>0$ and $A$ being a symmetric, positive semidefinite Matrix $Ain mathbb{R}^{n times n}$



      Is $M$ a $C^l$-Submanifold of $mathbb{R}^n$. If so, of which Dimension?










      share|cite|improve this question











      $endgroup$




      I have a huge problem solving this question. Does anybody have literature on this or maybe a solution?



      Let
      $
      M:={xin mathbb{R}^n : x^{⊤} A x = r} subset mathbb{R}^n
      $

      for $r>0$ and $A$ being a symmetric, positive semidefinite Matrix $Ain mathbb{R}^{n times n}$



      Is $M$ a $C^l$-Submanifold of $mathbb{R}^n$. If so, of which Dimension?







      analysis manifolds submanifold






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Jan 13 at 21:54







      KingDingeling

















      asked Jan 13 at 21:53









      KingDingelingKingDingeling

      1517




      1517






















          1 Answer
          1






          active

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          1












          $begingroup$

          There exists a symmetric positive semidefinite matrix $B$ such that $B^2=A$. Let $K$ denote the set of vectors $x$ such that $Bx=0$. Let $L$ be its orthogonal: $B$ induces an isomorphism on $L$.



          Then the linear isomorphism $mathbb{R}^n rightarrow K times L$ maps $M$ to $K times B^{-1}mathcal{S}_L(r)$. Thus $M$ is a submanifold of dimension $n-1$.






          share|cite|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thanks a lot. Is there maybe literature about this? Has this Set a name or something?
            $endgroup$
            – KingDingeling
            Jan 13 at 22:05






          • 1




            $begingroup$
            Not to my knowledge, but I am afraid I do not know much about the literature.
            $endgroup$
            – Mindlack
            Jan 13 at 22:53











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          1












          $begingroup$

          There exists a symmetric positive semidefinite matrix $B$ such that $B^2=A$. Let $K$ denote the set of vectors $x$ such that $Bx=0$. Let $L$ be its orthogonal: $B$ induces an isomorphism on $L$.



          Then the linear isomorphism $mathbb{R}^n rightarrow K times L$ maps $M$ to $K times B^{-1}mathcal{S}_L(r)$. Thus $M$ is a submanifold of dimension $n-1$.






          share|cite|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thanks a lot. Is there maybe literature about this? Has this Set a name or something?
            $endgroup$
            – KingDingeling
            Jan 13 at 22:05






          • 1




            $begingroup$
            Not to my knowledge, but I am afraid I do not know much about the literature.
            $endgroup$
            – Mindlack
            Jan 13 at 22:53
















          1












          $begingroup$

          There exists a symmetric positive semidefinite matrix $B$ such that $B^2=A$. Let $K$ denote the set of vectors $x$ such that $Bx=0$. Let $L$ be its orthogonal: $B$ induces an isomorphism on $L$.



          Then the linear isomorphism $mathbb{R}^n rightarrow K times L$ maps $M$ to $K times B^{-1}mathcal{S}_L(r)$. Thus $M$ is a submanifold of dimension $n-1$.






          share|cite|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Thanks a lot. Is there maybe literature about this? Has this Set a name or something?
            $endgroup$
            – KingDingeling
            Jan 13 at 22:05






          • 1




            $begingroup$
            Not to my knowledge, but I am afraid I do not know much about the literature.
            $endgroup$
            – Mindlack
            Jan 13 at 22:53














          1












          1








          1





          $begingroup$

          There exists a symmetric positive semidefinite matrix $B$ such that $B^2=A$. Let $K$ denote the set of vectors $x$ such that $Bx=0$. Let $L$ be its orthogonal: $B$ induces an isomorphism on $L$.



          Then the linear isomorphism $mathbb{R}^n rightarrow K times L$ maps $M$ to $K times B^{-1}mathcal{S}_L(r)$. Thus $M$ is a submanifold of dimension $n-1$.






          share|cite|improve this answer









          $endgroup$



          There exists a symmetric positive semidefinite matrix $B$ such that $B^2=A$. Let $K$ denote the set of vectors $x$ such that $Bx=0$. Let $L$ be its orthogonal: $B$ induces an isomorphism on $L$.



          Then the linear isomorphism $mathbb{R}^n rightarrow K times L$ maps $M$ to $K times B^{-1}mathcal{S}_L(r)$. Thus $M$ is a submanifold of dimension $n-1$.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 13 at 22:00









          MindlackMindlack

          4,450210




          4,450210








          • 1




            $begingroup$
            Thanks a lot. Is there maybe literature about this? Has this Set a name or something?
            $endgroup$
            – KingDingeling
            Jan 13 at 22:05






          • 1




            $begingroup$
            Not to my knowledge, but I am afraid I do not know much about the literature.
            $endgroup$
            – Mindlack
            Jan 13 at 22:53














          • 1




            $begingroup$
            Thanks a lot. Is there maybe literature about this? Has this Set a name or something?
            $endgroup$
            – KingDingeling
            Jan 13 at 22:05






          • 1




            $begingroup$
            Not to my knowledge, but I am afraid I do not know much about the literature.
            $endgroup$
            – Mindlack
            Jan 13 at 22:53








          1




          1




          $begingroup$
          Thanks a lot. Is there maybe literature about this? Has this Set a name or something?
          $endgroup$
          – KingDingeling
          Jan 13 at 22:05




          $begingroup$
          Thanks a lot. Is there maybe literature about this? Has this Set a name or something?
          $endgroup$
          – KingDingeling
          Jan 13 at 22:05




          1




          1




          $begingroup$
          Not to my knowledge, but I am afraid I do not know much about the literature.
          $endgroup$
          – Mindlack
          Jan 13 at 22:53




          $begingroup$
          Not to my knowledge, but I am afraid I do not know much about the literature.
          $endgroup$
          – Mindlack
          Jan 13 at 22:53


















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