A general method to determine limiting optimal shapes for edge-isoperimetric inequalities

Ellen Veomett¹ ; Emmanuel Tsukerman²

¹Saint Mary's College of California
²University of California, Berkeley

The electronic journal of combinatorics, Tome 24 (2017) no. 1

Résumé

For a general family of graphs on $\mathbb{Z}^n$, we translate the edge-isoperimetric problem into a continuous isoperimetric problem in $\mathbb{R}^n$. We then solve the continuous isoperimetric problem using the Brunn-Minkowski inequality and Minkowski's theorem on mixed volumes. This translation allows us to conclude, under a reasonable assumption about the discrete problem, that the shapes of the optimal sets in the discrete problem approach the shape of the optimal set in the continuous problem as the size of the set grows. The solution is the zonotope defined as the Minkowski sum of the edges of the original graph. We demonstrate the efficacy of this method by revisiting some previously solved classical edge-isoperimetric problems. We then apply our method to some discrete isoperimetric problems which had not previously been solved. The complexity of those solutions suggest that it would be quite difficult to find them using discrete methods only.

Détail

DOI : 10.37236/6403

Classification : 05C63, 05C12
Mots-clés : discrete isoperimetric problem, continuous isoperimetric problem, infinite graphs, lattices