- #1

ergospherical

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- Homework Statement
- See below

- Relevant Equations
- N/A

Say a model hamiltonian with unperturbed eigenvalues E

_{1}and E_{2}= E_{3}is subjected to a perturbation V such that V_{12}= V_{21}= x and V_{13}= V_{31}= x^{2}, with all other elements zero. I'm having trouble calculating the corrected eigenvalues. In the degenerate subspace spanned by |2> and |3> I need to diagonalise V, but all of these matrix elements are zero?