Perturbation method for low states of a many-particle boson system

Liquid 4He: Contributions to First Principles Theory. I. Quantized Vortices and Thermohydrodynamic Properties

“…A generalization of the two-factor wave function structure, containing a correlation factor that is either the ground state wave function or an approximation to it, is the defining feature of what is now called the correlated basis function (CBF) formalism [20,[35][36][37][38].…”

“…A multiple excitation model was developed by Jackson and Feenberg [36][37][38][39]. Starting with the space coordinate representation of the Hamiltonian and momentum operators, they evaluated the dominant contributions for matrix elements for an infinite set of CBF wave functions and subsequently diagonalized the Hamiltonian.…”

“…Starting with the space coordinate representation of the Hamiltonian and momentum operators, they evaluated the dominant contributions for matrix elements for an infinite set of CBF wave functions and subsequently diagonalized the Hamiltonian. The results they found included the Bijl-Feynman excitation spectrum for a realistic model of liquid 4 He [36][37][38] and the Bogoliubov results for weakly interacting, low-density systems [38][39]. The formulas they derived [36][37][38][39] are also applicable to a broad range of particle interaction strengths and particle densities.…”

“…The results they found included the Bijl-Feynman excitation spectrum for a realistic model of liquid 4 He [36][37][38] and the Bogoliubov results for weakly interacting, low-density systems [38][39]. The formulas they derived [36][37][38][39] are also applicable to a broad range of particle interaction strengths and particle densities. Their formulas and methods could be adapted and used in model studies for Bose-Einstein condensates in ultracold gases of sodium and other elements that are of current interest [40-45,45a].…”

“…Their formulas and methods could be adapted and used in model studies for Bose-Einstein condensates in ultracold gases of sodium and other elements that are of current interest [40-45,45a]. A unifying element in their work [36][37][38][39] that makes possible the simultaneous treatment of a broad range of physical systems is the generalized normalization integral. This integral was originally introduced by Iwamoto and Yamada [46] in nuclear physics.…”