Using network-flow techniques to solve an optimization problem from   surface-physics
  The solid-on-solid model provides a commonly used framework for the description of surfaces. In the last years it has been extended in order to investigate the effect of defects in the bulk on the roughness of the surface. The determination of the ground state of this model leads to a combinatorial problem, which is reduced to an uncapacitated, convex minimum-circulation problem. We will show that the successive shortest path algorithm solves the problem in polynomial time. 
U. Blasum, W. Hochst\"attler, C. Moll and H. Rieger