Frobenius Norm of Hadamard Product and Trace

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I'm trying to relate the Frobenius Norm of a Hadamard Product to a trace that does not include another Hadamard Product, if possible. In other words, if A and B are (sxr) matrices, with not all positive values,



$left||Acirc B right||^2_F = $?



I'm trying to relate the sum of the squares of all the entries of the Hadamard product. I know that the sum of all the entries of the Hadamard product are



$sum_i sum_j (Acirc B)_ij = tr(A B^T) $



and also



$left||Acirc B right||^2_F = tr((Acirc B)^T(Acirc B)) $



But I am trying to get $left||Acirc B right||^2_F $ in the form of the trace of some combination of A and B, without a Hadamard product. Even an inequality would help. I've tried various identities and inequalities related to Hadamard Product and Frobenius Norm, but I am not having any luck.



Any suggestions would be appreciated.







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    up vote
    1
    down vote

    favorite












    I'm trying to relate the Frobenius Norm of a Hadamard Product to a trace that does not include another Hadamard Product, if possible. In other words, if A and B are (sxr) matrices, with not all positive values,



    $left||Acirc B right||^2_F = $?



    I'm trying to relate the sum of the squares of all the entries of the Hadamard product. I know that the sum of all the entries of the Hadamard product are



    $sum_i sum_j (Acirc B)_ij = tr(A B^T) $



    and also



    $left||Acirc B right||^2_F = tr((Acirc B)^T(Acirc B)) $



    But I am trying to get $left||Acirc B right||^2_F $ in the form of the trace of some combination of A and B, without a Hadamard product. Even an inequality would help. I've tried various identities and inequalities related to Hadamard Product and Frobenius Norm, but I am not having any luck.



    Any suggestions would be appreciated.







    share|cite|improve this question





















      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      I'm trying to relate the Frobenius Norm of a Hadamard Product to a trace that does not include another Hadamard Product, if possible. In other words, if A and B are (sxr) matrices, with not all positive values,



      $left||Acirc B right||^2_F = $?



      I'm trying to relate the sum of the squares of all the entries of the Hadamard product. I know that the sum of all the entries of the Hadamard product are



      $sum_i sum_j (Acirc B)_ij = tr(A B^T) $



      and also



      $left||Acirc B right||^2_F = tr((Acirc B)^T(Acirc B)) $



      But I am trying to get $left||Acirc B right||^2_F $ in the form of the trace of some combination of A and B, without a Hadamard product. Even an inequality would help. I've tried various identities and inequalities related to Hadamard Product and Frobenius Norm, but I am not having any luck.



      Any suggestions would be appreciated.







      share|cite|improve this question











      I'm trying to relate the Frobenius Norm of a Hadamard Product to a trace that does not include another Hadamard Product, if possible. In other words, if A and B are (sxr) matrices, with not all positive values,



      $left||Acirc B right||^2_F = $?



      I'm trying to relate the sum of the squares of all the entries of the Hadamard product. I know that the sum of all the entries of the Hadamard product are



      $sum_i sum_j (Acirc B)_ij = tr(A B^T) $



      and also



      $left||Acirc B right||^2_F = tr((Acirc B)^T(Acirc B)) $



      But I am trying to get $left||Acirc B right||^2_F $ in the form of the trace of some combination of A and B, without a Hadamard product. Even an inequality would help. I've tried various identities and inequalities related to Hadamard Product and Frobenius Norm, but I am not having any luck.



      Any suggestions would be appreciated.









      share|cite|improve this question










      share|cite|improve this question




      share|cite|improve this question









      asked Jul 16 at 1:44









      Rich

      112




      112




















          1 Answer
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          Let
          $$eqalign
          D_a &= rm Diag(rm vec(A)) cr
          D_b &= rm Diag(rm vec(B)) cr
          $$
          Then
          $$eqalign_F^2
          &= $$






          share|cite|improve this answer





















          • Interesting solution, and that seems to work. Is there any way to relate this back to some multiple of the original A matrix? This is part of a larger problem I'm working.
            – Rich
            Jul 18 at 0:36










          • Note that every element of $A$ lies on the diagonal of $D_a$, and is therefore an eigenvalue of $D_a$. Functions like the determinant and trace are ultimately functions of the eigenvalues. The eigenvalues of a matrix are a different set than the elements of the matrix -- and smaller one since $(n<n^2)$. I don't see any obvious way to connect the eigenvalues with the individual elements. Another problem: simply rearranging the elements of $A$ will change its eigenvalues, whereas the eigenvalues of $D_a$ are unaffected by this.
            – greg
            Jul 18 at 2:07











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          1 Answer
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          1 Answer
          1






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          up vote
          0
          down vote













          Let
          $$eqalign
          D_a &= rm Diag(rm vec(A)) cr
          D_b &= rm Diag(rm vec(B)) cr
          $$
          Then
          $$eqalign_F^2
          &= $$






          share|cite|improve this answer





















          • Interesting solution, and that seems to work. Is there any way to relate this back to some multiple of the original A matrix? This is part of a larger problem I'm working.
            – Rich
            Jul 18 at 0:36










          • Note that every element of $A$ lies on the diagonal of $D_a$, and is therefore an eigenvalue of $D_a$. Functions like the determinant and trace are ultimately functions of the eigenvalues. The eigenvalues of a matrix are a different set than the elements of the matrix -- and smaller one since $(n<n^2)$. I don't see any obvious way to connect the eigenvalues with the individual elements. Another problem: simply rearranging the elements of $A$ will change its eigenvalues, whereas the eigenvalues of $D_a$ are unaffected by this.
            – greg
            Jul 18 at 2:07















          up vote
          0
          down vote













          Let
          $$eqalign
          D_a &= rm Diag(rm vec(A)) cr
          D_b &= rm Diag(rm vec(B)) cr
          $$
          Then
          $$eqalign_F^2
          &= $$






          share|cite|improve this answer





















          • Interesting solution, and that seems to work. Is there any way to relate this back to some multiple of the original A matrix? This is part of a larger problem I'm working.
            – Rich
            Jul 18 at 0:36










          • Note that every element of $A$ lies on the diagonal of $D_a$, and is therefore an eigenvalue of $D_a$. Functions like the determinant and trace are ultimately functions of the eigenvalues. The eigenvalues of a matrix are a different set than the elements of the matrix -- and smaller one since $(n<n^2)$. I don't see any obvious way to connect the eigenvalues with the individual elements. Another problem: simply rearranging the elements of $A$ will change its eigenvalues, whereas the eigenvalues of $D_a$ are unaffected by this.
            – greg
            Jul 18 at 2:07













          up vote
          0
          down vote










          up vote
          0
          down vote









          Let
          $$eqalign
          D_a &= rm Diag(rm vec(A)) cr
          D_b &= rm Diag(rm vec(B)) cr
          $$
          Then
          $$eqalign_F^2
          &= $$






          share|cite|improve this answer













          Let
          $$eqalign
          D_a &= rm Diag(rm vec(A)) cr
          D_b &= rm Diag(rm vec(B)) cr
          $$
          Then
          $$eqalign_F^2
          &= $$







          share|cite|improve this answer













          share|cite|improve this answer



          share|cite|improve this answer











          answered Jul 16 at 3:19









          greg

          5,7431715




          5,7431715











          • Interesting solution, and that seems to work. Is there any way to relate this back to some multiple of the original A matrix? This is part of a larger problem I'm working.
            – Rich
            Jul 18 at 0:36










          • Note that every element of $A$ lies on the diagonal of $D_a$, and is therefore an eigenvalue of $D_a$. Functions like the determinant and trace are ultimately functions of the eigenvalues. The eigenvalues of a matrix are a different set than the elements of the matrix -- and smaller one since $(n<n^2)$. I don't see any obvious way to connect the eigenvalues with the individual elements. Another problem: simply rearranging the elements of $A$ will change its eigenvalues, whereas the eigenvalues of $D_a$ are unaffected by this.
            – greg
            Jul 18 at 2:07

















          • Interesting solution, and that seems to work. Is there any way to relate this back to some multiple of the original A matrix? This is part of a larger problem I'm working.
            – Rich
            Jul 18 at 0:36










          • Note that every element of $A$ lies on the diagonal of $D_a$, and is therefore an eigenvalue of $D_a$. Functions like the determinant and trace are ultimately functions of the eigenvalues. The eigenvalues of a matrix are a different set than the elements of the matrix -- and smaller one since $(n<n^2)$. I don't see any obvious way to connect the eigenvalues with the individual elements. Another problem: simply rearranging the elements of $A$ will change its eigenvalues, whereas the eigenvalues of $D_a$ are unaffected by this.
            – greg
            Jul 18 at 2:07
















          Interesting solution, and that seems to work. Is there any way to relate this back to some multiple of the original A matrix? This is part of a larger problem I'm working.
          – Rich
          Jul 18 at 0:36




          Interesting solution, and that seems to work. Is there any way to relate this back to some multiple of the original A matrix? This is part of a larger problem I'm working.
          – Rich
          Jul 18 at 0:36












          Note that every element of $A$ lies on the diagonal of $D_a$, and is therefore an eigenvalue of $D_a$. Functions like the determinant and trace are ultimately functions of the eigenvalues. The eigenvalues of a matrix are a different set than the elements of the matrix -- and smaller one since $(n<n^2)$. I don't see any obvious way to connect the eigenvalues with the individual elements. Another problem: simply rearranging the elements of $A$ will change its eigenvalues, whereas the eigenvalues of $D_a$ are unaffected by this.
          – greg
          Jul 18 at 2:07





          Note that every element of $A$ lies on the diagonal of $D_a$, and is therefore an eigenvalue of $D_a$. Functions like the determinant and trace are ultimately functions of the eigenvalues. The eigenvalues of a matrix are a different set than the elements of the matrix -- and smaller one since $(n<n^2)$. I don't see any obvious way to connect the eigenvalues with the individual elements. Another problem: simply rearranging the elements of $A$ will change its eigenvalues, whereas the eigenvalues of $D_a$ are unaffected by this.
          – greg
          Jul 18 at 2:07













           

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