Journal of Statistical Physics, Vol. 42, Nos. 5/6, 1986. p. 743-798.
In this paper we study several problems in statistical mechanics involving systems of fluctuating extended objects, such as interacting steps and domain walls. We reconsider the roughening transition and relate it to the free energy of a gas of steps and to the rounding of facets in the equilibrium shape of crystals, defined via the Wulff construction. Using an idealized description due to Fisher and Fisher we analyze the commensurate-incommensurate transition in uniaxial systems in terms of a gas of interacting domain walls. We also study the interactions between a domain wall and a rigid wall and between two interfaces, a problem which is central for the understanding of wetting...