  We consider a lattice model of a semiflexible homopolymer chain in a bad
solvent. Beside the temperature $T$, this model is described by (i) a curvature
energy $\varepsilon_h$, representing the stiffness of the chain (ii) a
nearest-neighbour attractive energy $\varepsilon_v$, representing the solvent
(iii) the monomer density $\rho={N \over \Omega}$, where $N$ and $\Omega$
denote respectively the number of monomers and the number of lattice sites.
This model is a simplified view of the protein folding problem, which
encompasses the geometrical competition between secondary structures (the
curvature term modelling helix formation) and the global compactness (modeled
here by the attractive energy), but contains no side chain information...
