Trajectories of directed lattice paths

Abstract

The distribution of monomers along a linear polymer grafted on a hard wall is modelled by determining the probability distribution of occupied vertices of Dyck and ballot path models of adsorbing linear polymers. For example, the probability that a Dyck path passes through the lattice site with coordinates $(\lfloor \epsilon n \rfloor,\lfloor \delta \sqrt{n}\rfloor)$ in the square lattice, for $0 < \epsilon < 1$ and $\delta\geq 0$, is determined asymptotically as $n\to\infty$ and this uncovers the probability density of vertices along Dyck paths in the limit as the length of the path $n$ approaches infinity: $$\hbox{P}_r (\epsilon,\delta) = \frac{4\delta^2}{\sqrt{\pi\,\epsilon^3(1-\epsilon)^3}} \, e^{-\delta^2/\epsilon(1-\epsilon)}\ .$$ The properties of a polymer coating of a hard wall and the density or distribution of monomers in the coating is relevant in applications such as the stabilisation of a colloid dispersion by a polymer or in a drug delivery system such as a drug-eluding stent covered by a grafted polymer.