Similar Matrices have the same rank Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)prove the similar matrices have the same rankWhat subspace of 3 x 3 matrices is spanned by the invertible matrices? Rank 1 matrices? [GStrang P181, 3.5.29(a)(b)]Prove that matrices have equal rank.Can some one explain me a easy alternate proof of rank nullity theorem?Similar matrices of rank 1Two idempotent matrices are similar iff they have the same rankshow that a matrix a that is similar to an invertible matrix B is itself invertible. More generally, show that similar matrices have the same rank.Why “similar” matrices instead of “equivalent”?A and B are similar if and only if $textrank(A)=textrank(B)$?If $A$ is $ktimes l$ and $B$ is $ltimes k$, $lgeq k$ and full-rank, must $AB$ have full-rank?If real matrices $A,B$ have the same ch. polynomial and rank, and rk$(A-lambda I)= textrk(B-lambda I)$ for each eigenvalue, are they similar?

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Similar Matrices have the same rank



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)prove the similar matrices have the same rankWhat subspace of 3 x 3 matrices is spanned by the invertible matrices? Rank 1 matrices? [GStrang P181, 3.5.29(a)(b)]Prove that matrices have equal rank.Can some one explain me a easy alternate proof of rank nullity theorem?Similar matrices of rank 1Two idempotent matrices are similar iff they have the same rankshow that a matrix a that is similar to an invertible matrix B is itself invertible. More generally, show that similar matrices have the same rank.Why “similar” matrices instead of “equivalent”?A and B are similar if and only if $textrank(A)=textrank(B)$?If $A$ is $ktimes l$ and $B$ is $ltimes k$, $lgeq k$ and full-rank, must $AB$ have full-rank?If real matrices $A,B$ have the same ch. polynomial and rank, and rk$(A-lambda I)= textrk(B-lambda I)$ for each eigenvalue, are they similar?










0












$begingroup$


Prove that :- If $2$ matrices $A$ and $B$ are similar then they will have the same rank.



Proof is given here but I can't understand both answers which are related to image and kernel. I have seen all the video lectures of Prof. Gilbert Strang but I have not seen these things in those lectures. I only know that $A$ and $B$ are similar iff $A$ = $MBM^-1$ for some invertible square matrix $M$ but I can't proceed further. Is there any simple proof of it ?

Please help.










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    What definition of rank are you working with? Usually, rank is defined as the dimension of the image, so it's hard to talk about rank without talking about images...
    $endgroup$
    – 5xum
    Apr 2 at 8:37










  • $begingroup$
    Isn't the rank also the number of non zero eigen values? And similar matrices have the same spectrum
    $endgroup$
    – Fareed AF
    Apr 2 at 8:39






  • 1




    $begingroup$
    @FareedAF The rank is only the number of non zero eigen values if the matrices are square.
    $endgroup$
    – 5xum
    Apr 2 at 8:47










  • $begingroup$
    @5xum The OP is clearly talking about square matrices, otherwise the product $MBM^-1$ doesn’t make sense.
    $endgroup$
    – amd
    Apr 2 at 17:28















0












$begingroup$


Prove that :- If $2$ matrices $A$ and $B$ are similar then they will have the same rank.



Proof is given here but I can't understand both answers which are related to image and kernel. I have seen all the video lectures of Prof. Gilbert Strang but I have not seen these things in those lectures. I only know that $A$ and $B$ are similar iff $A$ = $MBM^-1$ for some invertible square matrix $M$ but I can't proceed further. Is there any simple proof of it ?

Please help.










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    What definition of rank are you working with? Usually, rank is defined as the dimension of the image, so it's hard to talk about rank without talking about images...
    $endgroup$
    – 5xum
    Apr 2 at 8:37










  • $begingroup$
    Isn't the rank also the number of non zero eigen values? And similar matrices have the same spectrum
    $endgroup$
    – Fareed AF
    Apr 2 at 8:39






  • 1




    $begingroup$
    @FareedAF The rank is only the number of non zero eigen values if the matrices are square.
    $endgroup$
    – 5xum
    Apr 2 at 8:47










  • $begingroup$
    @5xum The OP is clearly talking about square matrices, otherwise the product $MBM^-1$ doesn’t make sense.
    $endgroup$
    – amd
    Apr 2 at 17:28













0












0








0





$begingroup$


Prove that :- If $2$ matrices $A$ and $B$ are similar then they will have the same rank.



Proof is given here but I can't understand both answers which are related to image and kernel. I have seen all the video lectures of Prof. Gilbert Strang but I have not seen these things in those lectures. I only know that $A$ and $B$ are similar iff $A$ = $MBM^-1$ for some invertible square matrix $M$ but I can't proceed further. Is there any simple proof of it ?

Please help.










share|cite|improve this question









$endgroup$




Prove that :- If $2$ matrices $A$ and $B$ are similar then they will have the same rank.



Proof is given here but I can't understand both answers which are related to image and kernel. I have seen all the video lectures of Prof. Gilbert Strang but I have not seen these things in those lectures. I only know that $A$ and $B$ are similar iff $A$ = $MBM^-1$ for some invertible square matrix $M$ but I can't proceed further. Is there any simple proof of it ?

Please help.







linear-algebra matrix-rank






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Apr 2 at 8:33









ankitankit

1077




1077







  • 1




    $begingroup$
    What definition of rank are you working with? Usually, rank is defined as the dimension of the image, so it's hard to talk about rank without talking about images...
    $endgroup$
    – 5xum
    Apr 2 at 8:37










  • $begingroup$
    Isn't the rank also the number of non zero eigen values? And similar matrices have the same spectrum
    $endgroup$
    – Fareed AF
    Apr 2 at 8:39






  • 1




    $begingroup$
    @FareedAF The rank is only the number of non zero eigen values if the matrices are square.
    $endgroup$
    – 5xum
    Apr 2 at 8:47










  • $begingroup$
    @5xum The OP is clearly talking about square matrices, otherwise the product $MBM^-1$ doesn’t make sense.
    $endgroup$
    – amd
    Apr 2 at 17:28












  • 1




    $begingroup$
    What definition of rank are you working with? Usually, rank is defined as the dimension of the image, so it's hard to talk about rank without talking about images...
    $endgroup$
    – 5xum
    Apr 2 at 8:37










  • $begingroup$
    Isn't the rank also the number of non zero eigen values? And similar matrices have the same spectrum
    $endgroup$
    – Fareed AF
    Apr 2 at 8:39






  • 1




    $begingroup$
    @FareedAF The rank is only the number of non zero eigen values if the matrices are square.
    $endgroup$
    – 5xum
    Apr 2 at 8:47










  • $begingroup$
    @5xum The OP is clearly talking about square matrices, otherwise the product $MBM^-1$ doesn’t make sense.
    $endgroup$
    – amd
    Apr 2 at 17:28







1




1




$begingroup$
What definition of rank are you working with? Usually, rank is defined as the dimension of the image, so it's hard to talk about rank without talking about images...
$endgroup$
– 5xum
Apr 2 at 8:37




$begingroup$
What definition of rank are you working with? Usually, rank is defined as the dimension of the image, so it's hard to talk about rank without talking about images...
$endgroup$
– 5xum
Apr 2 at 8:37












$begingroup$
Isn't the rank also the number of non zero eigen values? And similar matrices have the same spectrum
$endgroup$
– Fareed AF
Apr 2 at 8:39




$begingroup$
Isn't the rank also the number of non zero eigen values? And similar matrices have the same spectrum
$endgroup$
– Fareed AF
Apr 2 at 8:39




1




1




$begingroup$
@FareedAF The rank is only the number of non zero eigen values if the matrices are square.
$endgroup$
– 5xum
Apr 2 at 8:47




$begingroup$
@FareedAF The rank is only the number of non zero eigen values if the matrices are square.
$endgroup$
– 5xum
Apr 2 at 8:47












$begingroup$
@5xum The OP is clearly talking about square matrices, otherwise the product $MBM^-1$ doesn’t make sense.
$endgroup$
– amd
Apr 2 at 17:28




$begingroup$
@5xum The OP is clearly talking about square matrices, otherwise the product $MBM^-1$ doesn’t make sense.
$endgroup$
– amd
Apr 2 at 17:28










1 Answer
1






active

oldest

votes


















3












$begingroup$

My favourite proof goes along the lines of




$rk(B)geq rk(MBM^-1) = rk(A)$, as multiplying can only reduce rank (or keep it unchanged), never increase it. Now note that $B = M^-1AM$, so we similarily get $rk(A)geq rk(M^-1AM) = rk(B)$







share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you! @Arthur
    $endgroup$
    – ankit
    Apr 2 at 8:57











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









3












$begingroup$

My favourite proof goes along the lines of




$rk(B)geq rk(MBM^-1) = rk(A)$, as multiplying can only reduce rank (or keep it unchanged), never increase it. Now note that $B = M^-1AM$, so we similarily get $rk(A)geq rk(M^-1AM) = rk(B)$







share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you! @Arthur
    $endgroup$
    – ankit
    Apr 2 at 8:57















3












$begingroup$

My favourite proof goes along the lines of




$rk(B)geq rk(MBM^-1) = rk(A)$, as multiplying can only reduce rank (or keep it unchanged), never increase it. Now note that $B = M^-1AM$, so we similarily get $rk(A)geq rk(M^-1AM) = rk(B)$







share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you! @Arthur
    $endgroup$
    – ankit
    Apr 2 at 8:57













3












3








3





$begingroup$

My favourite proof goes along the lines of




$rk(B)geq rk(MBM^-1) = rk(A)$, as multiplying can only reduce rank (or keep it unchanged), never increase it. Now note that $B = M^-1AM$, so we similarily get $rk(A)geq rk(M^-1AM) = rk(B)$







share|cite|improve this answer









$endgroup$



My favourite proof goes along the lines of




$rk(B)geq rk(MBM^-1) = rk(A)$, as multiplying can only reduce rank (or keep it unchanged), never increase it. Now note that $B = M^-1AM$, so we similarily get $rk(A)geq rk(M^-1AM) = rk(B)$








share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Apr 2 at 8:38









ArthurArthur

123k7122211




123k7122211











  • $begingroup$
    Thank you! @Arthur
    $endgroup$
    – ankit
    Apr 2 at 8:57
















  • $begingroup$
    Thank you! @Arthur
    $endgroup$
    – ankit
    Apr 2 at 8:57















$begingroup$
Thank you! @Arthur
$endgroup$
– ankit
Apr 2 at 8:57




$begingroup$
Thank you! @Arthur
$endgroup$
– ankit
Apr 2 at 8:57

















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