How to determine two matrices are conjugate.

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Which of the following statements are true?



  • The matrices $
    A=left[ beginarraycc
    1 & 1 \
    0 & 1\
    endarray right]$ and $
    B=left[ beginarraycc
    1 & 0 \
    1 & 1\
    endarray right]$ are conjugate in $GL_2(mathbbR)$

  • The matrices $
    A=left[ beginarraycc
    1 & 1 \
    0 & 1\
    endarray right]$ and $
    B=left[ beginarraycc
    1 & 0 \
    1 & 1\
    endarray right]$ are conjugate in $SL_2(mathbbR)$

  • The matrices $
    C=left[ beginarraycc
    1 & 0 \
    0 & 2\
    endarray right]$ and $
    D=left[ beginarraycc
    1 & 3 \
    0 & 2\
    endarray right]$ are conjugate in $GL_2(mathbbR)$

I know the conjugate matrices have the same eigenvalues. But all of this matrices have the same eigenvalues. I am not sure how to determine that which matrices are conjugate to each other.







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    up vote
    0
    down vote

    favorite












    Which of the following statements are true?



    • The matrices $
      A=left[ beginarraycc
      1 & 1 \
      0 & 1\
      endarray right]$ and $
      B=left[ beginarraycc
      1 & 0 \
      1 & 1\
      endarray right]$ are conjugate in $GL_2(mathbbR)$

    • The matrices $
      A=left[ beginarraycc
      1 & 1 \
      0 & 1\
      endarray right]$ and $
      B=left[ beginarraycc
      1 & 0 \
      1 & 1\
      endarray right]$ are conjugate in $SL_2(mathbbR)$

    • The matrices $
      C=left[ beginarraycc
      1 & 0 \
      0 & 2\
      endarray right]$ and $
      D=left[ beginarraycc
      1 & 3 \
      0 & 2\
      endarray right]$ are conjugate in $GL_2(mathbbR)$

    I know the conjugate matrices have the same eigenvalues. But all of this matrices have the same eigenvalues. I am not sure how to determine that which matrices are conjugate to each other.







    share|cite|improve this question





















      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      Which of the following statements are true?



      • The matrices $
        A=left[ beginarraycc
        1 & 1 \
        0 & 1\
        endarray right]$ and $
        B=left[ beginarraycc
        1 & 0 \
        1 & 1\
        endarray right]$ are conjugate in $GL_2(mathbbR)$

      • The matrices $
        A=left[ beginarraycc
        1 & 1 \
        0 & 1\
        endarray right]$ and $
        B=left[ beginarraycc
        1 & 0 \
        1 & 1\
        endarray right]$ are conjugate in $SL_2(mathbbR)$

      • The matrices $
        C=left[ beginarraycc
        1 & 0 \
        0 & 2\
        endarray right]$ and $
        D=left[ beginarraycc
        1 & 3 \
        0 & 2\
        endarray right]$ are conjugate in $GL_2(mathbbR)$

      I know the conjugate matrices have the same eigenvalues. But all of this matrices have the same eigenvalues. I am not sure how to determine that which matrices are conjugate to each other.







      share|cite|improve this question











      Which of the following statements are true?



      • The matrices $
        A=left[ beginarraycc
        1 & 1 \
        0 & 1\
        endarray right]$ and $
        B=left[ beginarraycc
        1 & 0 \
        1 & 1\
        endarray right]$ are conjugate in $GL_2(mathbbR)$

      • The matrices $
        A=left[ beginarraycc
        1 & 1 \
        0 & 1\
        endarray right]$ and $
        B=left[ beginarraycc
        1 & 0 \
        1 & 1\
        endarray right]$ are conjugate in $SL_2(mathbbR)$

      • The matrices $
        C=left[ beginarraycc
        1 & 0 \
        0 & 2\
        endarray right]$ and $
        D=left[ beginarraycc
        1 & 3 \
        0 & 2\
        endarray right]$ are conjugate in $GL_2(mathbbR)$

      I know the conjugate matrices have the same eigenvalues. But all of this matrices have the same eigenvalues. I am not sure how to determine that which matrices are conjugate to each other.









      share|cite|improve this question










      share|cite|improve this question




      share|cite|improve this question









      asked Jul 23 at 8:44









      Babai

      2,50021539




      2,50021539




















          1 Answer
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          Hint




          The definition of conjugacy is: if $A$ and $B$ are two matrices such that $$A= P^-1BP$$ then they are conjugate. In $GL(2,mathbbR)$ is the same as similarity so not only the eigenvalues have to be preserved: mainly two similar matrices in $GL(2,mathbbR)$ have the same Jordan normal form




          Notice that A is in Jordan canonical form (just look at the eigenvalues). Notice that the $D$ matrix is diagonalisable



          Probabily this forum Why aren't this two matrices conjugate in $SL(2,mathbbR)$ can help for the second question.






          share|cite|improve this answer





















          • What is $D$ here?
            – Babai
            Jul 23 at 9:15










          • Sorry, I'm indicating the matrices as they are on your worksheet $$ A=left[beginmatrix 1&1\0&1endmatrixright]$$ and $$ D=left[beginmatrix 1&3\0&2endmatrixright]$$
            – Davide Morgante
            Jul 23 at 9:17










          Your Answer




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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          0
          down vote













          Hint




          The definition of conjugacy is: if $A$ and $B$ are two matrices such that $$A= P^-1BP$$ then they are conjugate. In $GL(2,mathbbR)$ is the same as similarity so not only the eigenvalues have to be preserved: mainly two similar matrices in $GL(2,mathbbR)$ have the same Jordan normal form




          Notice that A is in Jordan canonical form (just look at the eigenvalues). Notice that the $D$ matrix is diagonalisable



          Probabily this forum Why aren't this two matrices conjugate in $SL(2,mathbbR)$ can help for the second question.






          share|cite|improve this answer





















          • What is $D$ here?
            – Babai
            Jul 23 at 9:15










          • Sorry, I'm indicating the matrices as they are on your worksheet $$ A=left[beginmatrix 1&1\0&1endmatrixright]$$ and $$ D=left[beginmatrix 1&3\0&2endmatrixright]$$
            – Davide Morgante
            Jul 23 at 9:17














          up vote
          0
          down vote













          Hint




          The definition of conjugacy is: if $A$ and $B$ are two matrices such that $$A= P^-1BP$$ then they are conjugate. In $GL(2,mathbbR)$ is the same as similarity so not only the eigenvalues have to be preserved: mainly two similar matrices in $GL(2,mathbbR)$ have the same Jordan normal form




          Notice that A is in Jordan canonical form (just look at the eigenvalues). Notice that the $D$ matrix is diagonalisable



          Probabily this forum Why aren't this two matrices conjugate in $SL(2,mathbbR)$ can help for the second question.






          share|cite|improve this answer





















          • What is $D$ here?
            – Babai
            Jul 23 at 9:15










          • Sorry, I'm indicating the matrices as they are on your worksheet $$ A=left[beginmatrix 1&1\0&1endmatrixright]$$ and $$ D=left[beginmatrix 1&3\0&2endmatrixright]$$
            – Davide Morgante
            Jul 23 at 9:17












          up vote
          0
          down vote










          up vote
          0
          down vote









          Hint




          The definition of conjugacy is: if $A$ and $B$ are two matrices such that $$A= P^-1BP$$ then they are conjugate. In $GL(2,mathbbR)$ is the same as similarity so not only the eigenvalues have to be preserved: mainly two similar matrices in $GL(2,mathbbR)$ have the same Jordan normal form




          Notice that A is in Jordan canonical form (just look at the eigenvalues). Notice that the $D$ matrix is diagonalisable



          Probabily this forum Why aren't this two matrices conjugate in $SL(2,mathbbR)$ can help for the second question.






          share|cite|improve this answer













          Hint




          The definition of conjugacy is: if $A$ and $B$ are two matrices such that $$A= P^-1BP$$ then they are conjugate. In $GL(2,mathbbR)$ is the same as similarity so not only the eigenvalues have to be preserved: mainly two similar matrices in $GL(2,mathbbR)$ have the same Jordan normal form




          Notice that A is in Jordan canonical form (just look at the eigenvalues). Notice that the $D$ matrix is diagonalisable



          Probabily this forum Why aren't this two matrices conjugate in $SL(2,mathbbR)$ can help for the second question.







          share|cite|improve this answer













          share|cite|improve this answer



          share|cite|improve this answer











          answered Jul 23 at 9:09









          Davide Morgante

          1,775220




          1,775220











          • What is $D$ here?
            – Babai
            Jul 23 at 9:15










          • Sorry, I'm indicating the matrices as they are on your worksheet $$ A=left[beginmatrix 1&1\0&1endmatrixright]$$ and $$ D=left[beginmatrix 1&3\0&2endmatrixright]$$
            – Davide Morgante
            Jul 23 at 9:17
















          • What is $D$ here?
            – Babai
            Jul 23 at 9:15










          • Sorry, I'm indicating the matrices as they are on your worksheet $$ A=left[beginmatrix 1&1\0&1endmatrixright]$$ and $$ D=left[beginmatrix 1&3\0&2endmatrixright]$$
            – Davide Morgante
            Jul 23 at 9:17















          What is $D$ here?
          – Babai
          Jul 23 at 9:15




          What is $D$ here?
          – Babai
          Jul 23 at 9:15












          Sorry, I'm indicating the matrices as they are on your worksheet $$ A=left[beginmatrix 1&1\0&1endmatrixright]$$ and $$ D=left[beginmatrix 1&3\0&2endmatrixright]$$
          – Davide Morgante
          Jul 23 at 9:17




          Sorry, I'm indicating the matrices as they are on your worksheet $$ A=left[beginmatrix 1&1\0&1endmatrixright]$$ and $$ D=left[beginmatrix 1&3\0&2endmatrixright]$$
          – Davide Morgante
          Jul 23 at 9:17












           

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