Time-dependent perturbation theory

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The discussion centers on the confusion surrounding time-dependent perturbation theory (TDPT) as presented in Sakurai's text. The main issue is understanding why one expands the state in the basis of the unperturbed Hamiltonian H0 when the system is described by the total Hamiltonian H = H0 + V. Participants clarify that the perturbation V is considered small, allowing for an iterative approach to solving the equations of motion for the coefficients in the state expansion. The conversation highlights that expanding in the basis of H0 is justified because these eigenkets form a complete basis, even if they do not directly describe the perturbed system. Ultimately, the discussion emphasizes the importance of recognizing the limitations of perturbation theory and the conditions under which it is applicable.
  • #51
I read those sections and i didnt find anything usefull. Please if you know the answer to the question just tell me..
I started another thread that is more relevant with my question.
 

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