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Alternative derivation of perturbation expansions in the projection operator formalism
Author(s) -
Timoneda J. Juanós I
Publication year - 1986
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560300308
Subject(s) - eigenvalues and eigenvectors , wave function , formalism (music) , perturbation (astronomy) , diagrammatic reasoning , operator (biology) , normalization (sociology) , poincaré–lindstedt method , mathematics , mathematical physics , mathematical analysis , physics , quantum mechanics , computer science , chemistry , art , musical , biochemistry , repressor , sociology , transcription factor , anthropology , visual arts , gene , programming language
The perturbation‐theoretic expansions obtained from Löwdin's projection operator formalism are derived in a new way, using Kato's formulation of perturbation theory. Kato's approach provides a convenient alternative to diagrammatic techniques for obtaining eigenvalues and eigenvectors. Different normalization criteria imposable on the wave function are easily visualized in terms of the operator that yields the perturbed state vector when it acts upon the unperturbed wave function.