Perturbation theory - slightly different approach

We have to solve the Schrodinger equation for the ground state H q = E with 

The Schrodinger equation does not force the normalization of the function. It is convenient to use the intermediate normalization (Fig. 10.1 l.a), i.e. to require that Aol Ao ) = 1- This means that the (non-normalized) must include the normalized function of zeroth order and, possibly, something orthogonal to it. 

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Unperturbed Hamiltonian Perturbation theory - slightly different approach Reduced resolvent or the almost inverse of )... 

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