The Jordan canonical form of the matrix

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How to find the Jordan canonical form of the matrix $A$ as a function of the complex parameter $q$:



$$A=beginbmatrix 0 & 3 & q \ 1 & 0 & 0 \ 0 & 1 & 0endbmatrix$$
I can find the characteristic equation where $L$ is an eigenvalue $L^3-3L-q=0$
What should I do next? Looking for roots according to the Cardano formula? Or is there another option?







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    How to find the Jordan canonical form of the matrix $A$ as a function of the complex parameter $q$:



    $$A=beginbmatrix 0 & 3 & q \ 1 & 0 & 0 \ 0 & 1 & 0endbmatrix$$
    I can find the characteristic equation where $L$ is an eigenvalue $L^3-3L-q=0$
    What should I do next? Looking for roots according to the Cardano formula? Or is there another option?







    share|cite|improve this question























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      How to find the Jordan canonical form of the matrix $A$ as a function of the complex parameter $q$:



      $$A=beginbmatrix 0 & 3 & q \ 1 & 0 & 0 \ 0 & 1 & 0endbmatrix$$
      I can find the characteristic equation where $L$ is an eigenvalue $L^3-3L-q=0$
      What should I do next? Looking for roots according to the Cardano formula? Or is there another option?







      share|cite|improve this question













      How to find the Jordan canonical form of the matrix $A$ as a function of the complex parameter $q$:



      $$A=beginbmatrix 0 & 3 & q \ 1 & 0 & 0 \ 0 & 1 & 0endbmatrix$$
      I can find the characteristic equation where $L$ is an eigenvalue $L^3-3L-q=0$
      What should I do next? Looking for roots according to the Cardano formula? Or is there another option?









      share|cite|improve this question












      share|cite|improve this question




      share|cite|improve this question








      edited Jul 17 at 22:47









      mechanodroid

      22.2k52041




      22.2k52041









      asked Jul 17 at 21:04









      Bella

      154




      154




















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          Two choices, really. For most values of $q$ the characteristic polynomial $L^3 - 3 L - q$ has three distinct roots, so the Jordan form is just diagonal. Not that there is any real chance of writing that all out.



          The other choice is when there are repeat eigenvalues. The polynomials over a field make a Euclidean ring, and we can try to find the GCD of the polynomial and its (formal) derivative, that being $3L^2 - 3 .$ This factors as $3(L+1)(L-1).$ The possible roots are $1$ and $-1.$



          The two special cases that might have non-diagonal Jordan form are then $q=2,$ which has one Jordan form, and then $q=-2,$ which has a different Jordan form. In both cases you can find all the eigenvalues without difficulty; finish those.






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            1 Answer
            1






            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            1
            down vote



            accepted










            Two choices, really. For most values of $q$ the characteristic polynomial $L^3 - 3 L - q$ has three distinct roots, so the Jordan form is just diagonal. Not that there is any real chance of writing that all out.



            The other choice is when there are repeat eigenvalues. The polynomials over a field make a Euclidean ring, and we can try to find the GCD of the polynomial and its (formal) derivative, that being $3L^2 - 3 .$ This factors as $3(L+1)(L-1).$ The possible roots are $1$ and $-1.$



            The two special cases that might have non-diagonal Jordan form are then $q=2,$ which has one Jordan form, and then $q=-2,$ which has a different Jordan form. In both cases you can find all the eigenvalues without difficulty; finish those.






            share|cite|improve this answer



























              up vote
              1
              down vote



              accepted










              Two choices, really. For most values of $q$ the characteristic polynomial $L^3 - 3 L - q$ has three distinct roots, so the Jordan form is just diagonal. Not that there is any real chance of writing that all out.



              The other choice is when there are repeat eigenvalues. The polynomials over a field make a Euclidean ring, and we can try to find the GCD of the polynomial and its (formal) derivative, that being $3L^2 - 3 .$ This factors as $3(L+1)(L-1).$ The possible roots are $1$ and $-1.$



              The two special cases that might have non-diagonal Jordan form are then $q=2,$ which has one Jordan form, and then $q=-2,$ which has a different Jordan form. In both cases you can find all the eigenvalues without difficulty; finish those.






              share|cite|improve this answer

























                up vote
                1
                down vote



                accepted







                up vote
                1
                down vote



                accepted






                Two choices, really. For most values of $q$ the characteristic polynomial $L^3 - 3 L - q$ has three distinct roots, so the Jordan form is just diagonal. Not that there is any real chance of writing that all out.



                The other choice is when there are repeat eigenvalues. The polynomials over a field make a Euclidean ring, and we can try to find the GCD of the polynomial and its (formal) derivative, that being $3L^2 - 3 .$ This factors as $3(L+1)(L-1).$ The possible roots are $1$ and $-1.$



                The two special cases that might have non-diagonal Jordan form are then $q=2,$ which has one Jordan form, and then $q=-2,$ which has a different Jordan form. In both cases you can find all the eigenvalues without difficulty; finish those.






                share|cite|improve this answer















                Two choices, really. For most values of $q$ the characteristic polynomial $L^3 - 3 L - q$ has three distinct roots, so the Jordan form is just diagonal. Not that there is any real chance of writing that all out.



                The other choice is when there are repeat eigenvalues. The polynomials over a field make a Euclidean ring, and we can try to find the GCD of the polynomial and its (formal) derivative, that being $3L^2 - 3 .$ This factors as $3(L+1)(L-1).$ The possible roots are $1$ and $-1.$



                The two special cases that might have non-diagonal Jordan form are then $q=2,$ which has one Jordan form, and then $q=-2,$ which has a different Jordan form. In both cases you can find all the eigenvalues without difficulty; finish those.







                share|cite|improve this answer















                share|cite|improve this answer



                share|cite|improve this answer








                edited Jul 17 at 23:51


























                answered Jul 17 at 23:30









                Will Jagy

                97.2k594196




                97.2k594196






















                     

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