arXiv:cond-mat/0408023 · Europhysics Letters (EPL)
Ground-state energy of a homogeneous Bose-Einstein condensate beyond Bogoliubov
Christoph Weiß, André Eckardt
Abstract
The standard calculations of the ground-state energy of a homogeneous Bose gas rely on approximations which are physically reasonable but difficult to control. Lieb and Yngvason ( Phys. Rev. Lett. 80 (1998) 2504) have proved rigorously that the commonly accepted leading-order term of the ground-state energy is correct in the zero-density limit. Here, strong indications are given that also the next-to-leading term is correct. It is shown that the first terms obtained in a perturbative treatment provide contributions which are lost in the Bogoliubov approach.