The extended Bose-Hubbard model in a quadratic trap potential is studied
using a finite-size density-matrix renormalization group method (DMRG). We
compute the boson density profiles, the local compressibility and the hopping
correlation functions. We observed the phase separation induced by the trap in
all the quantities studied and conclude that the local density approximation is
valid in the extended Bose-Hubbard model. From the plateaus obtained in the
local compressibility it was possible to obtain the phase diagram of the
homogeneous system which is in agreement with previous results.Comment: 14 pages, 11 figure