Prove that all complex eigenvalues of the operators of a unitary or orthogonal representation have modulus 1.












1












$begingroup$


The question is given below:




Let $T$ be an orthogonal or unitary representation of the group $G$. Prove that all complex eigenvalues of the operators $T(g)$, $g in G$ have modulus one.




But I do not know how the answer of it will differ from the answer given in this link:



Show that the eigenvalues of a unitary matrix have modulus $1$



And what are the relations between operators of orthogonal or unitary representation and unitary or orthogonal matrices?










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    That's weird: from your previous questions, it's clear that you can use MathJax, yet you still embedded the question in an image? Please format all questions in text and MathJax as much as possible, to help people search for your question.
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    – Theo Bendit
    Feb 1 at 1:43










  • $begingroup$
    Okay I am sorry @TheoBendit I will obey this rule as much as possible.
    $endgroup$
    – hopefully
    Feb 1 at 1:55










  • $begingroup$
    No worries. Images are primarily used to embed diagrams, or other things that might aid understanding that cannot be formatted.
    $endgroup$
    – Theo Bendit
    Feb 1 at 1:57
















1












$begingroup$


The question is given below:




Let $T$ be an orthogonal or unitary representation of the group $G$. Prove that all complex eigenvalues of the operators $T(g)$, $g in G$ have modulus one.




But I do not know how the answer of it will differ from the answer given in this link:



Show that the eigenvalues of a unitary matrix have modulus $1$



And what are the relations between operators of orthogonal or unitary representation and unitary or orthogonal matrices?










share|cite|improve this question











$endgroup$












  • $begingroup$
    That's weird: from your previous questions, it's clear that you can use MathJax, yet you still embedded the question in an image? Please format all questions in text and MathJax as much as possible, to help people search for your question.
    $endgroup$
    – Theo Bendit
    Feb 1 at 1:43










  • $begingroup$
    Okay I am sorry @TheoBendit I will obey this rule as much as possible.
    $endgroup$
    – hopefully
    Feb 1 at 1:55










  • $begingroup$
    No worries. Images are primarily used to embed diagrams, or other things that might aid understanding that cannot be formatted.
    $endgroup$
    – Theo Bendit
    Feb 1 at 1:57














1












1








1





$begingroup$


The question is given below:




Let $T$ be an orthogonal or unitary representation of the group $G$. Prove that all complex eigenvalues of the operators $T(g)$, $g in G$ have modulus one.




But I do not know how the answer of it will differ from the answer given in this link:



Show that the eigenvalues of a unitary matrix have modulus $1$



And what are the relations between operators of orthogonal or unitary representation and unitary or orthogonal matrices?










share|cite|improve this question











$endgroup$




The question is given below:




Let $T$ be an orthogonal or unitary representation of the group $G$. Prove that all complex eigenvalues of the operators $T(g)$, $g in G$ have modulus one.




But I do not know how the answer of it will differ from the answer given in this link:



Show that the eigenvalues of a unitary matrix have modulus $1$



And what are the relations between operators of orthogonal or unitary representation and unitary or orthogonal matrices?







linear-algebra functional-analysis operator-theory representation-theory orthogonal-matrices






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Feb 1 at 1:41









Theo Bendit

20.8k12354




20.8k12354










asked Feb 1 at 1:26









hopefullyhopefully

281215




281215












  • $begingroup$
    That's weird: from your previous questions, it's clear that you can use MathJax, yet you still embedded the question in an image? Please format all questions in text and MathJax as much as possible, to help people search for your question.
    $endgroup$
    – Theo Bendit
    Feb 1 at 1:43










  • $begingroup$
    Okay I am sorry @TheoBendit I will obey this rule as much as possible.
    $endgroup$
    – hopefully
    Feb 1 at 1:55










  • $begingroup$
    No worries. Images are primarily used to embed diagrams, or other things that might aid understanding that cannot be formatted.
    $endgroup$
    – Theo Bendit
    Feb 1 at 1:57


















  • $begingroup$
    That's weird: from your previous questions, it's clear that you can use MathJax, yet you still embedded the question in an image? Please format all questions in text and MathJax as much as possible, to help people search for your question.
    $endgroup$
    – Theo Bendit
    Feb 1 at 1:43










  • $begingroup$
    Okay I am sorry @TheoBendit I will obey this rule as much as possible.
    $endgroup$
    – hopefully
    Feb 1 at 1:55










  • $begingroup$
    No worries. Images are primarily used to embed diagrams, or other things that might aid understanding that cannot be formatted.
    $endgroup$
    – Theo Bendit
    Feb 1 at 1:57
















$begingroup$
That's weird: from your previous questions, it's clear that you can use MathJax, yet you still embedded the question in an image? Please format all questions in text and MathJax as much as possible, to help people search for your question.
$endgroup$
– Theo Bendit
Feb 1 at 1:43




$begingroup$
That's weird: from your previous questions, it's clear that you can use MathJax, yet you still embedded the question in an image? Please format all questions in text and MathJax as much as possible, to help people search for your question.
$endgroup$
– Theo Bendit
Feb 1 at 1:43












$begingroup$
Okay I am sorry @TheoBendit I will obey this rule as much as possible.
$endgroup$
– hopefully
Feb 1 at 1:55




$begingroup$
Okay I am sorry @TheoBendit I will obey this rule as much as possible.
$endgroup$
– hopefully
Feb 1 at 1:55












$begingroup$
No worries. Images are primarily used to embed diagrams, or other things that might aid understanding that cannot be formatted.
$endgroup$
– Theo Bendit
Feb 1 at 1:57




$begingroup$
No worries. Images are primarily used to embed diagrams, or other things that might aid understanding that cannot be formatted.
$endgroup$
– Theo Bendit
Feb 1 at 1:57










2 Answers
2






active

oldest

votes


















2





+50







$begingroup$

An orthogonal representation is a representation by orthogonal matrices. A unitary representation is a representation by unitary matrices. So it really is just a question about eigenvalues of such matrices.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    So you mean that the answer to the above question is the same as the answer in the link mentioned above?
    $endgroup$
    – hopefully
    Feb 3 at 2:56






  • 1




    $begingroup$
    Well, the question is the same as the one in the link. I haven't visited the link to see what the answer there says.
    $endgroup$
    – Gerry Myerson
    Feb 3 at 3:02



















1












$begingroup$

An orthogonal operator $A : Xrightarrow X$ on an inner product space $X$ satisfies $|Ax|=|x|$ for all $x$. If $A$ were to have an eigenvector $xneq 0$ with eigenvalue $lambda$, then $|lambda x|=|x|$ or $|lambda||x|=|x|$ would have to hold, which would force $|lambda|=1$.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    So you are saying that the above link does not contain the answer?
    $endgroup$
    – hopefully
    Feb 4 at 0:15












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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









2





+50







$begingroup$

An orthogonal representation is a representation by orthogonal matrices. A unitary representation is a representation by unitary matrices. So it really is just a question about eigenvalues of such matrices.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    So you mean that the answer to the above question is the same as the answer in the link mentioned above?
    $endgroup$
    – hopefully
    Feb 3 at 2:56






  • 1




    $begingroup$
    Well, the question is the same as the one in the link. I haven't visited the link to see what the answer there says.
    $endgroup$
    – Gerry Myerson
    Feb 3 at 3:02
















2





+50







$begingroup$

An orthogonal representation is a representation by orthogonal matrices. A unitary representation is a representation by unitary matrices. So it really is just a question about eigenvalues of such matrices.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    So you mean that the answer to the above question is the same as the answer in the link mentioned above?
    $endgroup$
    – hopefully
    Feb 3 at 2:56






  • 1




    $begingroup$
    Well, the question is the same as the one in the link. I haven't visited the link to see what the answer there says.
    $endgroup$
    – Gerry Myerson
    Feb 3 at 3:02














2





+50







2





+50



2




+50



$begingroup$

An orthogonal representation is a representation by orthogonal matrices. A unitary representation is a representation by unitary matrices. So it really is just a question about eigenvalues of such matrices.






share|cite|improve this answer









$endgroup$



An orthogonal representation is a representation by orthogonal matrices. A unitary representation is a representation by unitary matrices. So it really is just a question about eigenvalues of such matrices.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Feb 3 at 2:52









Gerry MyersonGerry Myerson

148k8152306




148k8152306












  • $begingroup$
    So you mean that the answer to the above question is the same as the answer in the link mentioned above?
    $endgroup$
    – hopefully
    Feb 3 at 2:56






  • 1




    $begingroup$
    Well, the question is the same as the one in the link. I haven't visited the link to see what the answer there says.
    $endgroup$
    – Gerry Myerson
    Feb 3 at 3:02


















  • $begingroup$
    So you mean that the answer to the above question is the same as the answer in the link mentioned above?
    $endgroup$
    – hopefully
    Feb 3 at 2:56






  • 1




    $begingroup$
    Well, the question is the same as the one in the link. I haven't visited the link to see what the answer there says.
    $endgroup$
    – Gerry Myerson
    Feb 3 at 3:02
















$begingroup$
So you mean that the answer to the above question is the same as the answer in the link mentioned above?
$endgroup$
– hopefully
Feb 3 at 2:56




$begingroup$
So you mean that the answer to the above question is the same as the answer in the link mentioned above?
$endgroup$
– hopefully
Feb 3 at 2:56




1




1




$begingroup$
Well, the question is the same as the one in the link. I haven't visited the link to see what the answer there says.
$endgroup$
– Gerry Myerson
Feb 3 at 3:02




$begingroup$
Well, the question is the same as the one in the link. I haven't visited the link to see what the answer there says.
$endgroup$
– Gerry Myerson
Feb 3 at 3:02











1












$begingroup$

An orthogonal operator $A : Xrightarrow X$ on an inner product space $X$ satisfies $|Ax|=|x|$ for all $x$. If $A$ were to have an eigenvector $xneq 0$ with eigenvalue $lambda$, then $|lambda x|=|x|$ or $|lambda||x|=|x|$ would have to hold, which would force $|lambda|=1$.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    So you are saying that the above link does not contain the answer?
    $endgroup$
    – hopefully
    Feb 4 at 0:15
















1












$begingroup$

An orthogonal operator $A : Xrightarrow X$ on an inner product space $X$ satisfies $|Ax|=|x|$ for all $x$. If $A$ were to have an eigenvector $xneq 0$ with eigenvalue $lambda$, then $|lambda x|=|x|$ or $|lambda||x|=|x|$ would have to hold, which would force $|lambda|=1$.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    So you are saying that the above link does not contain the answer?
    $endgroup$
    – hopefully
    Feb 4 at 0:15














1












1








1





$begingroup$

An orthogonal operator $A : Xrightarrow X$ on an inner product space $X$ satisfies $|Ax|=|x|$ for all $x$. If $A$ were to have an eigenvector $xneq 0$ with eigenvalue $lambda$, then $|lambda x|=|x|$ or $|lambda||x|=|x|$ would have to hold, which would force $|lambda|=1$.






share|cite|improve this answer









$endgroup$



An orthogonal operator $A : Xrightarrow X$ on an inner product space $X$ satisfies $|Ax|=|x|$ for all $x$. If $A$ were to have an eigenvector $xneq 0$ with eigenvalue $lambda$, then $|lambda x|=|x|$ or $|lambda||x|=|x|$ would have to hold, which would force $|lambda|=1$.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Feb 3 at 4:25









DisintegratingByPartsDisintegratingByParts

60.3k42681




60.3k42681












  • $begingroup$
    So you are saying that the above link does not contain the answer?
    $endgroup$
    – hopefully
    Feb 4 at 0:15


















  • $begingroup$
    So you are saying that the above link does not contain the answer?
    $endgroup$
    – hopefully
    Feb 4 at 0:15
















$begingroup$
So you are saying that the above link does not contain the answer?
$endgroup$
– hopefully
Feb 4 at 0:15




$begingroup$
So you are saying that the above link does not contain the answer?
$endgroup$
– hopefully
Feb 4 at 0:15


















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