  A surface model with skeletons is investigated by using the canonical Monte
Carlo simulations. The skeleton is composed of linear chains, which are joined
to each other at the rigid junctions. A one-dimensional bending energy is
defined on the linear chains, and no two-dimensional curvature energy is
assumed on the surface. The model undergoes a first-order transition between
the smooth phase and the crumpled phase. We conclude that the first-order
transition of the surface model with skeletons is independent of whether the
junctions are elastic or rigid.
