Correlations in systems of complex directed macromolecules

An ensemble of directed macromolecules on a lattice is considered, where the constituting molecules are chosen randomly with N different colours. Molecules of the same colour experience a hard-core (exclusion) interaction. We study the robustness of the macromolecules with respect to breaking and changing the colour of a constituting molecule, using a 1/N expansion. The properties depend strongly on the density of macromolecules. In particular, the macromolecules are robust against breaking and changing the colour at high densities but fragile at intermediate densities