Two-dimensional weakly interacting Bose gas: equation of state
G. E. Astrakharchik, J. Boronat, J. Casulleras, I. L. Kurbakov, Yu. E. Lozovik
备注：
New data points added at smaller densities. Correspondingly Table I, Figs. 1 and 2 are updated. Results by L. Pricoupenko (Ref [15]) are given in Table II. Comment [25] by Y. Castin is added. Minor changes in response to referee comments
The equation of state of a weakly interacting two-dimensional Bose gas is studied at zero temperature by means of quantum Monte Carlo methods. Going down to as low densities as na^2 ~ 10^{-100} permits us for the first time to obtain agreement on beyond mean-field level between predictions of perturbative methods and direct many-body numerical simulation, thus providing an answer to the fundamental question of the equation of state of a two-dimensional dilute Bose gas in the universal regime (i.e. entirely described by the gas parameter na^2). We also show that the measure of the frequency of a breathing collective oscillation in a trap at very low densities can be used to test the universal equation of state of a two-dimensional Bose gas.
Entanglement spectrum: Identification of the transition from vortex-liquid to vortex-lattice state in a weakly interacting rotating Bose-Einstein condensate
