title: Ground state energy of the two-dimensional weakly interacting Bose gas: first correction beyond Bogoliubov theory.
abstract: We consider the grand potential Omega of a two-dimensional weakly interacting homogeneous Bose gas at zero temperature. Building on a number-conserving Bogoliubov method for a lattice model in the grand canonical ensemble, we calculate the next order term as compared to the Bogoliubov prediction, in a systematic expansion of Omega in powers of the parameter measuring the weakness of the interaction. Our prediction is in very good agreement with recent Monte Carlo calculations.
authors.affiliation: Laboratoire Pierre Aigrain, Ecole Normale Supérieure and CNRS, Université Denis Diderot 7 and UPMC, 24 rue Lhomond, 75005 Paris, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Mora
authors.forename: Yvan
authors.initials: Y
authors.lastname: Castin