11-11U

A complete solution of the ground-state problem and an analysis of ground states for the Ising model in a magnetic field on the anisotropic triangular lattice with the nearest-neighbor interactions are presented. It is shown that this problem can be reduced to the ground-state problem for an infinite chain with the interactions up to the second neighbors. In addition to already known ground-state structures (which correspond to full-dimensional regions in the parameter space of the model), new structures are found (at boundaries of these regions), in particular, zigzagging stripes similar to those observed experimentally in colloidal monolayers. For disordered structures the degree (dimensionality) of disorder is determined.