Factorized trace of matrix productName for diagonals of a matrixtrace of product of positive definite matrixtrace of matrix productmatrix product with trace zerotrace of a product of similar matricesEigenvalues of Matrix Product.Trace of matrix that is a product of 2 others.Name of matrix which is invariant in traceTrace of a matrix productTrace of symmetric matrix product

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Factorized trace of matrix product


Name for diagonals of a matrixtrace of product of positive definite matrixtrace of matrix productmatrix product with trace zerotrace of a product of similar matricesEigenvalues of Matrix Product.Trace of matrix that is a product of 2 others.Name of matrix which is invariant in traceTrace of a matrix productTrace of symmetric matrix product













0












$begingroup$


Are there any particular types of matrices for which: $tr(AB)=tr(A)tr(B)$.










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    $1times 1$ matrices?
    $endgroup$
    – Lord Shark the Unknown
    Mar 15 at 6:15










  • $begingroup$
    Thanks, are there any other classes?
    $endgroup$
    – freude
    Mar 16 at 3:00






  • 1




    $begingroup$
    Yes, such as the set of all upper triangular matrices with zero diagonals.
    $endgroup$
    – user1551
    Mar 16 at 3:11















0












$begingroup$


Are there any particular types of matrices for which: $tr(AB)=tr(A)tr(B)$.










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    $1times 1$ matrices?
    $endgroup$
    – Lord Shark the Unknown
    Mar 15 at 6:15










  • $begingroup$
    Thanks, are there any other classes?
    $endgroup$
    – freude
    Mar 16 at 3:00






  • 1




    $begingroup$
    Yes, such as the set of all upper triangular matrices with zero diagonals.
    $endgroup$
    – user1551
    Mar 16 at 3:11













0












0








0





$begingroup$


Are there any particular types of matrices for which: $tr(AB)=tr(A)tr(B)$.










share|cite|improve this question









$endgroup$




Are there any particular types of matrices for which: $tr(AB)=tr(A)tr(B)$.







linear-algebra matrices






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Mar 15 at 5:07









freudefreude

1516




1516







  • 1




    $begingroup$
    $1times 1$ matrices?
    $endgroup$
    – Lord Shark the Unknown
    Mar 15 at 6:15










  • $begingroup$
    Thanks, are there any other classes?
    $endgroup$
    – freude
    Mar 16 at 3:00






  • 1




    $begingroup$
    Yes, such as the set of all upper triangular matrices with zero diagonals.
    $endgroup$
    – user1551
    Mar 16 at 3:11












  • 1




    $begingroup$
    $1times 1$ matrices?
    $endgroup$
    – Lord Shark the Unknown
    Mar 15 at 6:15










  • $begingroup$
    Thanks, are there any other classes?
    $endgroup$
    – freude
    Mar 16 at 3:00






  • 1




    $begingroup$
    Yes, such as the set of all upper triangular matrices with zero diagonals.
    $endgroup$
    – user1551
    Mar 16 at 3:11







1




1




$begingroup$
$1times 1$ matrices?
$endgroup$
– Lord Shark the Unknown
Mar 15 at 6:15




$begingroup$
$1times 1$ matrices?
$endgroup$
– Lord Shark the Unknown
Mar 15 at 6:15












$begingroup$
Thanks, are there any other classes?
$endgroup$
– freude
Mar 16 at 3:00




$begingroup$
Thanks, are there any other classes?
$endgroup$
– freude
Mar 16 at 3:00




1




1




$begingroup$
Yes, such as the set of all upper triangular matrices with zero diagonals.
$endgroup$
– user1551
Mar 16 at 3:11




$begingroup$
Yes, such as the set of all upper triangular matrices with zero diagonals.
$endgroup$
– user1551
Mar 16 at 3:11










1 Answer
1






active

oldest

votes


















0












$begingroup$

$$tr(AB)=tr(A)tr(B)$$
$$Sigma_j,i a_ji b_ij=Sigma_j,i a_jj b_ii$$



$$Sigma_j,i a_ji b_ij - a_jj b_ii=0$$



From here I am trying to find a class of matrices. To start with, let us assume that we are dealing with diagonal matrices only.



$$Sigma_j,i a_ji b_ij delta_ij - a_jj b_ii=0$$



For 2x2 matrices:



$$a_11 b_11 + a_22 b_22 - (a_11 + a_22)(b_11 + b_22)=0$$
$$-a_11 b_22 - a_22 b_11 =0$$
$$-a_11 b_22 = a_22 b_11$$






share|cite|improve this answer









$endgroup$












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    1 Answer
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    active

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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    0












    $begingroup$

    $$tr(AB)=tr(A)tr(B)$$
    $$Sigma_j,i a_ji b_ij=Sigma_j,i a_jj b_ii$$



    $$Sigma_j,i a_ji b_ij - a_jj b_ii=0$$



    From here I am trying to find a class of matrices. To start with, let us assume that we are dealing with diagonal matrices only.



    $$Sigma_j,i a_ji b_ij delta_ij - a_jj b_ii=0$$



    For 2x2 matrices:



    $$a_11 b_11 + a_22 b_22 - (a_11 + a_22)(b_11 + b_22)=0$$
    $$-a_11 b_22 - a_22 b_11 =0$$
    $$-a_11 b_22 = a_22 b_11$$






    share|cite|improve this answer









    $endgroup$

















      0












      $begingroup$

      $$tr(AB)=tr(A)tr(B)$$
      $$Sigma_j,i a_ji b_ij=Sigma_j,i a_jj b_ii$$



      $$Sigma_j,i a_ji b_ij - a_jj b_ii=0$$



      From here I am trying to find a class of matrices. To start with, let us assume that we are dealing with diagonal matrices only.



      $$Sigma_j,i a_ji b_ij delta_ij - a_jj b_ii=0$$



      For 2x2 matrices:



      $$a_11 b_11 + a_22 b_22 - (a_11 + a_22)(b_11 + b_22)=0$$
      $$-a_11 b_22 - a_22 b_11 =0$$
      $$-a_11 b_22 = a_22 b_11$$






      share|cite|improve this answer









      $endgroup$















        0












        0








        0





        $begingroup$

        $$tr(AB)=tr(A)tr(B)$$
        $$Sigma_j,i a_ji b_ij=Sigma_j,i a_jj b_ii$$



        $$Sigma_j,i a_ji b_ij - a_jj b_ii=0$$



        From here I am trying to find a class of matrices. To start with, let us assume that we are dealing with diagonal matrices only.



        $$Sigma_j,i a_ji b_ij delta_ij - a_jj b_ii=0$$



        For 2x2 matrices:



        $$a_11 b_11 + a_22 b_22 - (a_11 + a_22)(b_11 + b_22)=0$$
        $$-a_11 b_22 - a_22 b_11 =0$$
        $$-a_11 b_22 = a_22 b_11$$






        share|cite|improve this answer









        $endgroup$



        $$tr(AB)=tr(A)tr(B)$$
        $$Sigma_j,i a_ji b_ij=Sigma_j,i a_jj b_ii$$



        $$Sigma_j,i a_ji b_ij - a_jj b_ii=0$$



        From here I am trying to find a class of matrices. To start with, let us assume that we are dealing with diagonal matrices only.



        $$Sigma_j,i a_ji b_ij delta_ij - a_jj b_ii=0$$



        For 2x2 matrices:



        $$a_11 b_11 + a_22 b_22 - (a_11 + a_22)(b_11 + b_22)=0$$
        $$-a_11 b_22 - a_22 b_11 =0$$
        $$-a_11 b_22 = a_22 b_11$$







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Mar 16 at 2:52









        freudefreude

        1516




        1516



























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