We study the high density region of QCD within an effective model obtained in
the frame of the hopping parameter expansion. The model still acknowledges the
sign problem peculiar to non-zero chemical potential, but it permits the
development of refined algorithms which ensure a good overlap of the Monte
Carlo ensemble with the true one. We review the main features of the model,
including the most explicit form of the resumed expansion, and present
calculations concerning the dependence of various observables on the chemical
potential and on the temperature, in particular of the charge density and the
diquark susceptibility, which may be used to characterize the various phases
expected at high baryonic density.Comment: 6 pages, 5 figures, Lattice'05 proceedings, PoS styl
