  We study the phase structure of a 4D complex scalar field theory with a
potential V(Phi) = | Lambda^3 / Phi - Lambda Phi |^2 at zero and at finite
temperature. The model is analyzed by mean field and Monte Carlo methods. At
zero temperature the theory falls in the universality class of the 4D Ising
model when varying Lambda. The situation is less clear-cut for variations
w.r.t. Lambda at large temperatures and variations w.r.t. temperature at a
given value of Lambda. We observe temperature independence of the mass of the
first excitation.
