Eigenvalues of $ST$ and $TS$ The Next CEO of Stack OverflowEigenvalues and eigenvectors in physics?If $m_1,m_2$ are the minimal polynomials of $ST$ and $TS$ prove $m_2(x)=x^im_1(x)$ where $i=-1,0$ or $1$Finding Eigenvalues and Eigenspaces of Linear OperartorsIf a linear transformation is similar to another, then they have the same eigenvalues.Is the following proof that if $T: V rightarrow V$ as eigenvalue $lambda$, then $aT$ has eigenvalue $alambda$ correctLinear dependency and eigenvaluesProperties of eigenvalues/eigenvectorsEigenvalues-Eigenvectors and Rotation (in $mathbbR^2$)Finding all eigenvalues and eigenvectors by proofingeigenvalues Linear Transformation proof

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Eigenvalues of $ST$ and $TS$



The Next CEO of Stack OverflowEigenvalues and eigenvectors in physics?If $m_1,m_2$ are the minimal polynomials of $ST$ and $TS$ prove $m_2(x)=x^im_1(x)$ where $i=-1,0$ or $1$Finding Eigenvalues and Eigenspaces of Linear OperartorsIf a linear transformation is similar to another, then they have the same eigenvalues.Is the following proof that if $T: V rightarrow V$ as eigenvalue $lambda$, then $aT$ has eigenvalue $alambda$ correctLinear dependency and eigenvaluesProperties of eigenvalues/eigenvectorsEigenvalues-Eigenvectors and Rotation (in $mathbbR^2$)Finding all eigenvalues and eigenvectors by proofingeigenvalues Linear Transformation proof










0












$begingroup$


Given linear transformations $S,T:V→V$, prove that if $x=0$ is an eigenvalue of $ST$, then it is an eigenvalue of $TS$.



Secondly, prove that if $yneq 0$ is an eigenvalue of $ST$, and that if $v$ is eigenvector of $ST$ for $y$, then $Tv$ is an eigenvector of $TS$ for $y$.










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$endgroup$











  • $begingroup$
    What have you tried?
    $endgroup$
    – K.Power
    Mar 27 at 18:25










  • $begingroup$
    In future please use MathJax to format your posts.
    $endgroup$
    – K.Power
    Mar 27 at 18:29










  • $begingroup$
    Anyone can help?
    $endgroup$
    – ga as
    Mar 27 at 19:50










  • $begingroup$
    You're more likely to get an answer if you provide some context, such as showing any ideas you have
    $endgroup$
    – K.Power
    Mar 27 at 19:51















0












$begingroup$


Given linear transformations $S,T:V→V$, prove that if $x=0$ is an eigenvalue of $ST$, then it is an eigenvalue of $TS$.



Secondly, prove that if $yneq 0$ is an eigenvalue of $ST$, and that if $v$ is eigenvector of $ST$ for $y$, then $Tv$ is an eigenvector of $TS$ for $y$.










share|cite|improve this question











$endgroup$











  • $begingroup$
    What have you tried?
    $endgroup$
    – K.Power
    Mar 27 at 18:25










  • $begingroup$
    In future please use MathJax to format your posts.
    $endgroup$
    – K.Power
    Mar 27 at 18:29










  • $begingroup$
    Anyone can help?
    $endgroup$
    – ga as
    Mar 27 at 19:50










  • $begingroup$
    You're more likely to get an answer if you provide some context, such as showing any ideas you have
    $endgroup$
    – K.Power
    Mar 27 at 19:51













0












0








0





$begingroup$


Given linear transformations $S,T:V→V$, prove that if $x=0$ is an eigenvalue of $ST$, then it is an eigenvalue of $TS$.



Secondly, prove that if $yneq 0$ is an eigenvalue of $ST$, and that if $v$ is eigenvector of $ST$ for $y$, then $Tv$ is an eigenvector of $TS$ for $y$.










share|cite|improve this question











$endgroup$




Given linear transformations $S,T:V→V$, prove that if $x=0$ is an eigenvalue of $ST$, then it is an eigenvalue of $TS$.



Secondly, prove that if $yneq 0$ is an eigenvalue of $ST$, and that if $v$ is eigenvector of $ST$ for $y$, then $Tv$ is an eigenvector of $TS$ for $y$.







eigenvalues-eigenvectors






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Mar 27 at 18:53









K.Power

3,630926




3,630926










asked Mar 27 at 18:20









ga asga as

72




72











  • $begingroup$
    What have you tried?
    $endgroup$
    – K.Power
    Mar 27 at 18:25










  • $begingroup$
    In future please use MathJax to format your posts.
    $endgroup$
    – K.Power
    Mar 27 at 18:29










  • $begingroup$
    Anyone can help?
    $endgroup$
    – ga as
    Mar 27 at 19:50










  • $begingroup$
    You're more likely to get an answer if you provide some context, such as showing any ideas you have
    $endgroup$
    – K.Power
    Mar 27 at 19:51
















  • $begingroup$
    What have you tried?
    $endgroup$
    – K.Power
    Mar 27 at 18:25










  • $begingroup$
    In future please use MathJax to format your posts.
    $endgroup$
    – K.Power
    Mar 27 at 18:29










  • $begingroup$
    Anyone can help?
    $endgroup$
    – ga as
    Mar 27 at 19:50










  • $begingroup$
    You're more likely to get an answer if you provide some context, such as showing any ideas you have
    $endgroup$
    – K.Power
    Mar 27 at 19:51















$begingroup$
What have you tried?
$endgroup$
– K.Power
Mar 27 at 18:25




$begingroup$
What have you tried?
$endgroup$
– K.Power
Mar 27 at 18:25












$begingroup$
In future please use MathJax to format your posts.
$endgroup$
– K.Power
Mar 27 at 18:29




$begingroup$
In future please use MathJax to format your posts.
$endgroup$
– K.Power
Mar 27 at 18:29












$begingroup$
Anyone can help?
$endgroup$
– ga as
Mar 27 at 19:50




$begingroup$
Anyone can help?
$endgroup$
– ga as
Mar 27 at 19:50












$begingroup$
You're more likely to get an answer if you provide some context, such as showing any ideas you have
$endgroup$
– K.Power
Mar 27 at 19:51




$begingroup$
You're more likely to get an answer if you provide some context, such as showing any ideas you have
$endgroup$
– K.Power
Mar 27 at 19:51










1 Answer
1






active

oldest

votes


















1












$begingroup$

For this first part, there may be a simpler approach, but this is what came to mind. Since $ST$ has zero as an eigenvalue, we have
$$det S det T = det ST = 0.$$
So, either $S$ or $T$ (or both) is singular. If $S$ is singular, take $v_0 neq 0$ so that $Sv_0=0$. Then,
$$TSv_0 = Tvec0 = vec0.$$
Suppose $T$ is singular. If $S$ is also singular, then, by the above, we are done. Suppose $S$ is not singular. Take $v_0 neq 0$ so that $Tv_0 = 0$ and pick $w_0$ so that $Sw_0=v_0$.



For the next part,
$$TS(Tv) = T(STv) = T(yv) = yTv,$$
which implies that $Tv$ is an eigenvector of $TS$ with corresponding eigenvalue $y$.






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    1 Answer
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    1 Answer
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    active

    oldest

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    1












    $begingroup$

    For this first part, there may be a simpler approach, but this is what came to mind. Since $ST$ has zero as an eigenvalue, we have
    $$det S det T = det ST = 0.$$
    So, either $S$ or $T$ (or both) is singular. If $S$ is singular, take $v_0 neq 0$ so that $Sv_0=0$. Then,
    $$TSv_0 = Tvec0 = vec0.$$
    Suppose $T$ is singular. If $S$ is also singular, then, by the above, we are done. Suppose $S$ is not singular. Take $v_0 neq 0$ so that $Tv_0 = 0$ and pick $w_0$ so that $Sw_0=v_0$.



    For the next part,
    $$TS(Tv) = T(STv) = T(yv) = yTv,$$
    which implies that $Tv$ is an eigenvector of $TS$ with corresponding eigenvalue $y$.






    share|cite|improve this answer











    $endgroup$

















      1












      $begingroup$

      For this first part, there may be a simpler approach, but this is what came to mind. Since $ST$ has zero as an eigenvalue, we have
      $$det S det T = det ST = 0.$$
      So, either $S$ or $T$ (or both) is singular. If $S$ is singular, take $v_0 neq 0$ so that $Sv_0=0$. Then,
      $$TSv_0 = Tvec0 = vec0.$$
      Suppose $T$ is singular. If $S$ is also singular, then, by the above, we are done. Suppose $S$ is not singular. Take $v_0 neq 0$ so that $Tv_0 = 0$ and pick $w_0$ so that $Sw_0=v_0$.



      For the next part,
      $$TS(Tv) = T(STv) = T(yv) = yTv,$$
      which implies that $Tv$ is an eigenvector of $TS$ with corresponding eigenvalue $y$.






      share|cite|improve this answer











      $endgroup$















        1












        1








        1





        $begingroup$

        For this first part, there may be a simpler approach, but this is what came to mind. Since $ST$ has zero as an eigenvalue, we have
        $$det S det T = det ST = 0.$$
        So, either $S$ or $T$ (or both) is singular. If $S$ is singular, take $v_0 neq 0$ so that $Sv_0=0$. Then,
        $$TSv_0 = Tvec0 = vec0.$$
        Suppose $T$ is singular. If $S$ is also singular, then, by the above, we are done. Suppose $S$ is not singular. Take $v_0 neq 0$ so that $Tv_0 = 0$ and pick $w_0$ so that $Sw_0=v_0$.



        For the next part,
        $$TS(Tv) = T(STv) = T(yv) = yTv,$$
        which implies that $Tv$ is an eigenvector of $TS$ with corresponding eigenvalue $y$.






        share|cite|improve this answer











        $endgroup$



        For this first part, there may be a simpler approach, but this is what came to mind. Since $ST$ has zero as an eigenvalue, we have
        $$det S det T = det ST = 0.$$
        So, either $S$ or $T$ (or both) is singular. If $S$ is singular, take $v_0 neq 0$ so that $Sv_0=0$. Then,
        $$TSv_0 = Tvec0 = vec0.$$
        Suppose $T$ is singular. If $S$ is also singular, then, by the above, we are done. Suppose $S$ is not singular. Take $v_0 neq 0$ so that $Tv_0 = 0$ and pick $w_0$ so that $Sw_0=v_0$.



        For the next part,
        $$TS(Tv) = T(STv) = T(yv) = yTv,$$
        which implies that $Tv$ is an eigenvector of $TS$ with corresponding eigenvalue $y$.







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Mar 27 at 20:05

























        answered Mar 27 at 19:54









        Gary MoonGary Moon

        92127




        92127



























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