Finding eigenvalues, Shankar exercise 1.8.3

TimID
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First, I appologise if this is in the wrong place, while the book is QM, the question is pure maths. Also I'm not sure if this techically counts as homework as I am self studying. Finally, sorry for the poor formatting, I'm not that good with LaTeX

Homework Statement



Given the matrix: \Omega =
\left[ {\begin{array}{ccc}<br /> 2 &amp; 0 &amp; 0 \\<br /> 0 &amp; 3 &amp; -1 \\<br /> 0 &amp; -1 &amp; 3 \\<br /> \end{array} } \right]<br />

Show that \omega1 = \omega2 = 1; \omega3 = 2

Homework Equations


The Attempt at a Solution



So det(\Omega - \omegaI) = (2 - \omega)((3 - \omega)(3 - \omega) - 1)

Which obviously leaves \omega = 2, but also (3 - \omega)2 = 1, the solutions to which should be \omega = 2 and \omega = 4.

Where am I going wrong?

Any help greatfully appreciated.
 
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You're not going wrong for the given matrix. Are you sure you're doing the right problem?
 
You're absolutely right, there was a factor of a half in the original question that I completely missed, thanks. I must have checked the original problem a dozen times before posting and didn't spot it, I hate my brain sometimes.

Thanks again,

Tim
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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