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ABSTRACT:
A model describing an ensemble of disjoint clusters on a square
lattice is introduced. In addition to the usual surface energy
terms, ex and
ey, the model includes
a bending energy ec per
corner in the interface. It is formulated as a seven-vertex model
which is in general not solvable. For b
ec= ln(2)/2, however, this seven-vertex
model becomes a free fermionic one and an exact expression for its
free energy is derived. In the extreme anisotropic (`Hamiltonian')
limit the operator content coincides with that of the 1D Ising model
in a transverse field. Three critical lines with Ising-like
behavior are found.
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