On the submodular matrix representation of a digraph

  • Authors:
  • Arlette Gaillard;Heinz Groeflin;Alan J. Hoffman;William R. Pulleyblank

  • Affiliations:
  • Institute of Operations Research, ETH-Zurich, CH-8092 Zurich, Switzerland;Institute of Informatics, University of Fribourg, Rue Faucigny 2, CH-1700 Fribourg, Switzerland;IBM Thomas J. Watson Research Center, Yorktown Heights, NY;IBM Thomas J. Watson Research Center, Yorktown Heights, NY

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2002

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Abstract

We reexamine the class of (0,±1) matrices called submodular, which we introduced in (Ann. Discrete Math. 15 (1982) 189). Our key idea in this paper is to define, for each submodular matrix M, a corresponding digraph G whose nodes are the columns of M. Our principal results are as follows: (a) a graph-theoretic interpretation of the polyhedron P(M) = {x: x ≥ 0, Mx ≥ - 1}, and (b) for a given G, the description of a submodular matrix contained in all submodular matrices representing G.