2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/124162The ground-state phase diagram of a two-dimensional Bose system with dipole-dipole interactions is studied by means of quantum Monte Carlo technique. Our calculation predicts a quantum phase transition from gas to solid phase when the density increases. In the gas phase the condensate fraction is calculated as a function of the density. Using Feynman approximation, the collective excitation branch is studied and appearance of a roton minimum is observed. Results of the static structure factor at both sides of the gas-solid phase are also presented. The Lindeman ratio at the transition point comes to be $γ= 0.230(6)$. The condensate fraction in the gas phase is estimated as a function of the density.4 figures v.3 One citation added, updated Fig.4. Minor changes following referee's and editor's commentsSuperconductivitytext