Fluctuation-induced attraction between adhesion sites of supported membranes

We use scaling arguments and coarse-grained Monte Carlo simulations to study the fluctuation-mediated interactions between a pair of adhesion sites of a bilayer membrane and a supporting surface. We find that the potential of mean force is an infinitely long range attractive potential that grows logarithmically with the pair distance r: phi((r) over right arrow)/k(B)T=c ln r, where the constant c=2 and c=1 for nonstressed and stressed membranes, respectively. When, in addition to excluded volume repulsion, the membrane also interacts with the underlying surface through a height-dependent attractive potential, the potential phi((r) over right arrow) is screened at large pair distances.