Convergence enhancement in perturbation theory

Research output: Article

5 Citations (Scopus)


The Frobenius norm of operator QW is minimized with respect to level shift parameters applied to the zero-order spectrum, where W is the perturbation while Q is the reduced resolvent of the zero-order Hamiltonian. The stationary condition leads to a simple formula for the level shifts which eliminates degeneracy-induced singularities. Such level shifts may increase the radius of convergence of the perturbation series, and may improve low-order perturbative estimations - as it is found in the cases of a simple matrix eigenvalue problem and the one-dimensional quartic anharmonic oscillator.

Original languageEnglish
Pages (from-to)105-120
Number of pages16
JournalCollection of Czechoslovak Chemical Communications
Issue number1
Publication statusPublished - jan. 2004

ASJC Scopus subject areas

  • Chemistry(all)

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