Hurlbert's Pebbling Page. Forcing (mathematics) Forcing is equivalent to the method of Boolean-valued models, which some feel is conceptually more natural and intuitive, but usually much more difficult to apply. identify with , and then introduce an expanded membership relation involving the "new" sets of the form .

Forcing is a more elaborate version of this idea, reducing the expansion to the existence of one new set, and allowing for fine control over the properties of the expanded universe. Change in the average geodesic distance of a graph when flipping a single edge. Cesar A. Hidalgo, Homepage.