Prove $|tr(PAP') - tr(PBP')| leq ||A-B||_{infty} ||P'||_1^2$












1












$begingroup$


How can I show the following identity?



$|text{tr}(PAP') - text{tr}(PBP')| leq ||A-B||_{infty} ||P'||_1^2$










share|cite|improve this question









$endgroup$








  • 3




    $begingroup$
    What is $P$ (and what happened to him)?
    $endgroup$
    – lcv
    Jan 25 at 1:07










  • $begingroup$
    @lcv: $P$ is a matrix that I am interested in estimating. I am not sure what you are trying to mean by "what happened to him"?
    $endgroup$
    – shani
    Jan 25 at 1:20










  • $begingroup$
    What is the relationship between $P$ and $P'$?
    $endgroup$
    – Kenny Wong
    Jan 25 at 8:16










  • $begingroup$
    $P'$ is the transpose of $P$.
    $endgroup$
    – shani
    Jan 25 at 8:18
















1












$begingroup$


How can I show the following identity?



$|text{tr}(PAP') - text{tr}(PBP')| leq ||A-B||_{infty} ||P'||_1^2$










share|cite|improve this question









$endgroup$








  • 3




    $begingroup$
    What is $P$ (and what happened to him)?
    $endgroup$
    – lcv
    Jan 25 at 1:07










  • $begingroup$
    @lcv: $P$ is a matrix that I am interested in estimating. I am not sure what you are trying to mean by "what happened to him"?
    $endgroup$
    – shani
    Jan 25 at 1:20










  • $begingroup$
    What is the relationship between $P$ and $P'$?
    $endgroup$
    – Kenny Wong
    Jan 25 at 8:16










  • $begingroup$
    $P'$ is the transpose of $P$.
    $endgroup$
    – shani
    Jan 25 at 8:18














1












1








1


0



$begingroup$


How can I show the following identity?



$|text{tr}(PAP') - text{tr}(PBP')| leq ||A-B||_{infty} ||P'||_1^2$










share|cite|improve this question









$endgroup$




How can I show the following identity?



$|text{tr}(PAP') - text{tr}(PBP')| leq ||A-B||_{infty} ||P'||_1^2$







linear-algebra norm






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 25 at 0:37









shanishani

1458




1458








  • 3




    $begingroup$
    What is $P$ (and what happened to him)?
    $endgroup$
    – lcv
    Jan 25 at 1:07










  • $begingroup$
    @lcv: $P$ is a matrix that I am interested in estimating. I am not sure what you are trying to mean by "what happened to him"?
    $endgroup$
    – shani
    Jan 25 at 1:20










  • $begingroup$
    What is the relationship between $P$ and $P'$?
    $endgroup$
    – Kenny Wong
    Jan 25 at 8:16










  • $begingroup$
    $P'$ is the transpose of $P$.
    $endgroup$
    – shani
    Jan 25 at 8:18














  • 3




    $begingroup$
    What is $P$ (and what happened to him)?
    $endgroup$
    – lcv
    Jan 25 at 1:07










  • $begingroup$
    @lcv: $P$ is a matrix that I am interested in estimating. I am not sure what you are trying to mean by "what happened to him"?
    $endgroup$
    – shani
    Jan 25 at 1:20










  • $begingroup$
    What is the relationship between $P$ and $P'$?
    $endgroup$
    – Kenny Wong
    Jan 25 at 8:16










  • $begingroup$
    $P'$ is the transpose of $P$.
    $endgroup$
    – shani
    Jan 25 at 8:18








3




3




$begingroup$
What is $P$ (and what happened to him)?
$endgroup$
– lcv
Jan 25 at 1:07




$begingroup$
What is $P$ (and what happened to him)?
$endgroup$
– lcv
Jan 25 at 1:07












$begingroup$
@lcv: $P$ is a matrix that I am interested in estimating. I am not sure what you are trying to mean by "what happened to him"?
$endgroup$
– shani
Jan 25 at 1:20




$begingroup$
@lcv: $P$ is a matrix that I am interested in estimating. I am not sure what you are trying to mean by "what happened to him"?
$endgroup$
– shani
Jan 25 at 1:20












$begingroup$
What is the relationship between $P$ and $P'$?
$endgroup$
– Kenny Wong
Jan 25 at 8:16




$begingroup$
What is the relationship between $P$ and $P'$?
$endgroup$
– Kenny Wong
Jan 25 at 8:16












$begingroup$
$P'$ is the transpose of $P$.
$endgroup$
– shani
Jan 25 at 8:18




$begingroup$
$P'$ is the transpose of $P$.
$endgroup$
– shani
Jan 25 at 8:18










1 Answer
1






active

oldest

votes


















2












$begingroup$

You have
$$
|text{tr}(PAP') - text{tr}(PBP')|=|text{tr}(PAP'-PBP')|=|text{tr}(P(A-B)P')|=|text{tr}((A-B)P'P)|.
$$

Now you apply the well-known Hölder inequality
$$
|text{tr}(XY)|leq |X|_infty,|Y|_1.
$$



If you don't see it, here are more details. From the above, you get
$$
|text{tr}(PAP') - text{tr}(PBP')|leq|A-B|_infty,|P'P|_1.
$$

With ${mu_j}$ the singular values of $P$, you have $$|P'P|_1=sum_jmu_j^2leqleft(sum_jmu_jright)^2=|P|_1^2.$$






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Is there a type in the Holder's inequality? What happened to Y? I can't see how this can be used to prove the upper bound
    $endgroup$
    – shani
    Jan 25 at 2:05










  • $begingroup$
    Yes, the second one was a $Y$.
    $endgroup$
    – Martin Argerami
    Jan 25 at 2:05











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1 Answer
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1 Answer
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2












$begingroup$

You have
$$
|text{tr}(PAP') - text{tr}(PBP')|=|text{tr}(PAP'-PBP')|=|text{tr}(P(A-B)P')|=|text{tr}((A-B)P'P)|.
$$

Now you apply the well-known Hölder inequality
$$
|text{tr}(XY)|leq |X|_infty,|Y|_1.
$$



If you don't see it, here are more details. From the above, you get
$$
|text{tr}(PAP') - text{tr}(PBP')|leq|A-B|_infty,|P'P|_1.
$$

With ${mu_j}$ the singular values of $P$, you have $$|P'P|_1=sum_jmu_j^2leqleft(sum_jmu_jright)^2=|P|_1^2.$$






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Is there a type in the Holder's inequality? What happened to Y? I can't see how this can be used to prove the upper bound
    $endgroup$
    – shani
    Jan 25 at 2:05










  • $begingroup$
    Yes, the second one was a $Y$.
    $endgroup$
    – Martin Argerami
    Jan 25 at 2:05
















2












$begingroup$

You have
$$
|text{tr}(PAP') - text{tr}(PBP')|=|text{tr}(PAP'-PBP')|=|text{tr}(P(A-B)P')|=|text{tr}((A-B)P'P)|.
$$

Now you apply the well-known Hölder inequality
$$
|text{tr}(XY)|leq |X|_infty,|Y|_1.
$$



If you don't see it, here are more details. From the above, you get
$$
|text{tr}(PAP') - text{tr}(PBP')|leq|A-B|_infty,|P'P|_1.
$$

With ${mu_j}$ the singular values of $P$, you have $$|P'P|_1=sum_jmu_j^2leqleft(sum_jmu_jright)^2=|P|_1^2.$$






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Is there a type in the Holder's inequality? What happened to Y? I can't see how this can be used to prove the upper bound
    $endgroup$
    – shani
    Jan 25 at 2:05










  • $begingroup$
    Yes, the second one was a $Y$.
    $endgroup$
    – Martin Argerami
    Jan 25 at 2:05














2












2








2





$begingroup$

You have
$$
|text{tr}(PAP') - text{tr}(PBP')|=|text{tr}(PAP'-PBP')|=|text{tr}(P(A-B)P')|=|text{tr}((A-B)P'P)|.
$$

Now you apply the well-known Hölder inequality
$$
|text{tr}(XY)|leq |X|_infty,|Y|_1.
$$



If you don't see it, here are more details. From the above, you get
$$
|text{tr}(PAP') - text{tr}(PBP')|leq|A-B|_infty,|P'P|_1.
$$

With ${mu_j}$ the singular values of $P$, you have $$|P'P|_1=sum_jmu_j^2leqleft(sum_jmu_jright)^2=|P|_1^2.$$






share|cite|improve this answer











$endgroup$



You have
$$
|text{tr}(PAP') - text{tr}(PBP')|=|text{tr}(PAP'-PBP')|=|text{tr}(P(A-B)P')|=|text{tr}((A-B)P'P)|.
$$

Now you apply the well-known Hölder inequality
$$
|text{tr}(XY)|leq |X|_infty,|Y|_1.
$$



If you don't see it, here are more details. From the above, you get
$$
|text{tr}(PAP') - text{tr}(PBP')|leq|A-B|_infty,|P'P|_1.
$$

With ${mu_j}$ the singular values of $P$, you have $$|P'P|_1=sum_jmu_j^2leqleft(sum_jmu_jright)^2=|P|_1^2.$$







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Jan 25 at 3:52

























answered Jan 25 at 1:36









Martin ArgeramiMartin Argerami

128k1184184




128k1184184












  • $begingroup$
    Is there a type in the Holder's inequality? What happened to Y? I can't see how this can be used to prove the upper bound
    $endgroup$
    – shani
    Jan 25 at 2:05










  • $begingroup$
    Yes, the second one was a $Y$.
    $endgroup$
    – Martin Argerami
    Jan 25 at 2:05


















  • $begingroup$
    Is there a type in the Holder's inequality? What happened to Y? I can't see how this can be used to prove the upper bound
    $endgroup$
    – shani
    Jan 25 at 2:05










  • $begingroup$
    Yes, the second one was a $Y$.
    $endgroup$
    – Martin Argerami
    Jan 25 at 2:05
















$begingroup$
Is there a type in the Holder's inequality? What happened to Y? I can't see how this can be used to prove the upper bound
$endgroup$
– shani
Jan 25 at 2:05




$begingroup$
Is there a type in the Holder's inequality? What happened to Y? I can't see how this can be used to prove the upper bound
$endgroup$
– shani
Jan 25 at 2:05












$begingroup$
Yes, the second one was a $Y$.
$endgroup$
– Martin Argerami
Jan 25 at 2:05




$begingroup$
Yes, the second one was a $Y$.
$endgroup$
– Martin Argerami
Jan 25 at 2:05


















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