Journal of Statistical Physics, Vol. 76, Nos. 3/4, 1994, p. 835-856.
A phase diagram is mapped out for a 2(1/2)-dimensional vortex lattice model in which vortex filaments lie in a plane, while both the velocity field and the Green function are three-dimensional. Both positive and negative" temperatures are considered. Various qualitative properties of turbulent states and of the superfluid lambda transition are well verified within the limitations of the model; the percolation properties of vortex transitions are exhibited; the differences between superfluid and classical vortex motion are highlighted, as is the importance of topological constraints in vortex dynamics; an earlier model of intermittency is verified.