Properties of the one-dimensional Bose–Hubbard model from a high-order perturbative expansion

We employ a high-order perturbative expansion to characterize the ground state of the Mott phase of the one-dimensional Bose–Hubbard model. We compute for different integer filling factors the energy per lattice site, the two-point and density–density correlations, and expectation values of powers of the on-site number operator determining the local atom number fluctuations (variance, skewness, kurtosis). We compare these expansions to numerical simulations of the infinite-size system to determine their range of applicability. We also discuss a new sum rule for the density–density correlations that can be used in both equilibrium and non-equilibrium systems. (paper)