  Few-body correlations often express the distinguishing characteristic
features of a many-body system. This thesis studies such correlations within
dilute Bose-Einstein condensates in the case of arbitrary negative s-wave
scattering length. The N-boson problem is solved by using an ab-initio approach
based on correlated Gaussians that allows explicit inclusion of few-body
correlations with a computational complexity that is independent of the number
of particles. Calculations introducing all higher-order correlations are also
done for small systems. In the weakly interacting regime, two-body correlations
are not only the simplest but also the most important. By varying the
scattering length and comparing the ground state energy for different
explicitly correlated trial wave functions this assumption is investigated
under both weakly and strongly interacting conditions.
