Improved optimization of perturbation theory: Applications to the oscillator energy levels and Bose-Einstein condensate critical temperature Auteur(s): Kneur J.-L., Neveu A., Pinto Marcus (Article) Publié: Physical Review A: Atomic, Molecular And Optical Physics, vol. 69 p.053624 (2004) Texte intégral en Openaccess : Ref HAL: hal-00259672_v1 Ref Arxiv: cond-mat/0401324 DOI: 10.1103/PhysRevA.69.053624 WoS: 000221813700139 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote 50 Citations Résumé: Improving perturbation theory via a variational optimization has generally produced in higher orders an embarrassingly large set of solutions, most of them unphysical (complex). We introduce an extension of the optimized perturbation method which leads to a drastic reduction of the number of acceptable solutions. The properties of this new method are studied and it is then applied to the calculation of relevant quantities in different $\phi^4$ models, such as the anharmonic oscillator energy levels and the critical Bose-Einstein Condensation temperature shift $\Delta T_c$ recently investigated by various authors. Our present estimates of $\Delta T_c$, incorporating the most recently available six and seven loop perturbative information, are in excellent agreement with all the available lattice numerical simulations. This represents a very substantial improvement over previous treatments. Commentaires: 9 pages |