-Ok..Let,s be the Hamiltonian [tex] H=H_0 +W [/tex] in one dimension where W is a "weak" term so we can apply perturbation theory.(adsbygoogle = window.adsbygoogle || []).push({});

-The "problem" comes when we need to calculate the eigenvalues and eigenfunction of H0 of course we set the system in an "imaginary potential well of width L" so we have the set of eigen-values-functions:

[tex] E_n =P^{2}/2m [/tex] [tex] p=(n\pi \hbar)/L [/tex] [tex] \Phi(x) =e^{in\pi x/L} [/tex]

the problem is...what is the value of L?...so when doing calculations..what,s the value of the width of our "imaginary" well..if we set L--->oo then the Energies and Wave functions tend all to 0.

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# Conceptual problem with perturbation theory

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