A variant of the Brillouin-Wigner perturbation theory with Epstein-Nesbet partitioning

2013/07/16 by Sangyoub Lee, Cheol Ho Choi, Lee, Sangyoub +5
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #FOS: Physical sciences #Quantum Mechanics and Applications #Quantum Physics (quant-ph) #Quantum optics and atomic interactions #quant-ph

paper · pdf · doi:10.48550/arxiv.1307.4238

15 pages

arxiv created 2013/07/16 · openalex publication_date 2013/07/16 · arxiv updated 2013/07/17 · openalex created_date 2022/10/01 · openalex updated_date 2026/07/28

Abstract

We present an elementary pedagogical derivation of the Brillouin-Wigner and the Rayleigh-Schrödinger perturbation theories with Epstein-Nesbet partitioning. A variant of the Brillouin-Wigner perturbation theory is also introduced, which can be easily extended to the quasi-degenerate case. A main advantage of the new theory is that the computing time required for obtaining the successive higher-order results is negligible after the third-order calculation. We illustrate the accuracy of the new perturbation theory for some simple model systems like the perturbed harmonic oscillator and the particle in a box.

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