Approximately Packing Dijoins Via Nowhere-Zero Flows

Abstract: In a digraph, a dicut is a cut where all the arcs cross in one direction. A dijoin is a subset of arcs that intersects each dicut. Woodall conjectured in 1976 that in every digraph, the minimum size of a dicut equals to the maximum number of disjoint dijoins. By building connections with nowhere-zero k-flows, we prove that every digraph with minimum dicut size $\tau$ contains $\lfloor \tau/k \rfloor$ disjoint dijoins if the underlying undirected graph admits a nowhere-zero k-flow. Joint work with Gérard Cornuéjols (CMU) and Siyue Liu (CMU)

Bio: Dr. Ravi is the Vasantrao Dempo Professor of Operations Research and Computer Science at Carnegie Mellon University. His research is on models, methods and applications of discrete optimization and their application to business and technological systems. He has published widely in diverse areas ranging from theoretical computer science to Operations and Marketing. In Computer Science, his main research interests are in approximation algorithms and network optimization.