Multiclass open queueing networks find wide applications in communication, computer and fabrication networks. Often one is interested in steady state performance measures associated with these systems.

Computer scientists defined the Strahler number of a binary tree in relation with  the minimum number of registers needed for the computation of an arithmetical expression.

Markets are of course, one of the oldest mechanism of exchanging commodities and cultural artifacts. While their history is over 5000 years old, their mathematical theory is rather recent. The first such models were by Fisher and Walras.

How does one partition the vertex set of a graph into two parts $(S,S^C)$, so that the ratio of edges going across to the Volume (number of edges incident on vertices in S) in the vertex set is as small as possible?