Gershgorin Circle theorem- implications











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(I am considering only real matrices)



Does only hold that if the area of all Gershgorin Circles is positiv $Rightarrow$ the Matrix is positiv definit (trivial)



or does also follow the vice versa



the Matrix is positiv definit $Rightarrow$ the area of all Gershgorin Circles is positiv










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    up vote
    1
    down vote

    favorite












    (I am considering only real matrices)



    Does only hold that if the area of all Gershgorin Circles is positiv $Rightarrow$ the Matrix is positiv definit (trivial)



    or does also follow the vice versa



    the Matrix is positiv definit $Rightarrow$ the area of all Gershgorin Circles is positiv










    share|cite|improve this question
























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      (I am considering only real matrices)



      Does only hold that if the area of all Gershgorin Circles is positiv $Rightarrow$ the Matrix is positiv definit (trivial)



      or does also follow the vice versa



      the Matrix is positiv definit $Rightarrow$ the area of all Gershgorin Circles is positiv










      share|cite|improve this question













      (I am considering only real matrices)



      Does only hold that if the area of all Gershgorin Circles is positiv $Rightarrow$ the Matrix is positiv definit (trivial)



      or does also follow the vice versa



      the Matrix is positiv definit $Rightarrow$ the area of all Gershgorin Circles is positiv







      matrices gershgorin-sets






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Nov 20 at 9:59









      baxbear

      397




      397






















          1 Answer
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          up vote
          2
          down vote



          accepted










          The reverse direction does not hold:
          $$
          A=pmatrix{ 1 & 2\ 2 & 10}
          $$

          is positive definite, but the Gershgorin circle for the first row contains numbers with negative real part.






          share|cite|improve this answer





















          • Thanks, I found something like it for special matrices in my old exercise papers and was wondering if I can use it to check if a $LL^T$ Cholesky decomposition is possible, seems it is not the case, thanks
            – baxbear
            Nov 20 at 10:17











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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          2
          down vote



          accepted










          The reverse direction does not hold:
          $$
          A=pmatrix{ 1 & 2\ 2 & 10}
          $$

          is positive definite, but the Gershgorin circle for the first row contains numbers with negative real part.






          share|cite|improve this answer





















          • Thanks, I found something like it for special matrices in my old exercise papers and was wondering if I can use it to check if a $LL^T$ Cholesky decomposition is possible, seems it is not the case, thanks
            – baxbear
            Nov 20 at 10:17















          up vote
          2
          down vote



          accepted










          The reverse direction does not hold:
          $$
          A=pmatrix{ 1 & 2\ 2 & 10}
          $$

          is positive definite, but the Gershgorin circle for the first row contains numbers with negative real part.






          share|cite|improve this answer





















          • Thanks, I found something like it for special matrices in my old exercise papers and was wondering if I can use it to check if a $LL^T$ Cholesky decomposition is possible, seems it is not the case, thanks
            – baxbear
            Nov 20 at 10:17













          up vote
          2
          down vote



          accepted







          up vote
          2
          down vote



          accepted






          The reverse direction does not hold:
          $$
          A=pmatrix{ 1 & 2\ 2 & 10}
          $$

          is positive definite, but the Gershgorin circle for the first row contains numbers with negative real part.






          share|cite|improve this answer












          The reverse direction does not hold:
          $$
          A=pmatrix{ 1 & 2\ 2 & 10}
          $$

          is positive definite, but the Gershgorin circle for the first row contains numbers with negative real part.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Nov 20 at 10:13









          daw

          23.8k1544




          23.8k1544












          • Thanks, I found something like it for special matrices in my old exercise papers and was wondering if I can use it to check if a $LL^T$ Cholesky decomposition is possible, seems it is not the case, thanks
            – baxbear
            Nov 20 at 10:17


















          • Thanks, I found something like it for special matrices in my old exercise papers and was wondering if I can use it to check if a $LL^T$ Cholesky decomposition is possible, seems it is not the case, thanks
            – baxbear
            Nov 20 at 10:17
















          Thanks, I found something like it for special matrices in my old exercise papers and was wondering if I can use it to check if a $LL^T$ Cholesky decomposition is possible, seems it is not the case, thanks
          – baxbear
          Nov 20 at 10:17




          Thanks, I found something like it for special matrices in my old exercise papers and was wondering if I can use it to check if a $LL^T$ Cholesky decomposition is possible, seems it is not the case, thanks
          – baxbear
          Nov 20 at 10:17


















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