Edge-Directions of Standard Polyhedra with Applications to Network Flows

  • Authors:
  • Shmuel Onn;Uriel G. Rothblum;Yoav Tangir

  • Affiliations:
  • Technion - Israel Institute of Technology, Haifa, Israel 32000;Technion - Israel Institute of Technology, Haifa, Israel 32000;Technion - Israel Institute of Technology, Haifa, Israel 32000

  • Venue:
  • Journal of Global Optimization
  • Year:
  • 2005

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Abstract

Recent results show that edge-directions of polyhedra play an important role in (combinatorial) optimization; in particular, a d-dimensional polyhedron with |D| distinct edge-directions has at most O(|D|d-1) vertices. Here, we obtain a characterization of the directions of edges that are adjacent to a given vertex of a standard polyhedron of the form P = {x : Ax = b, l驴 x驴 u, tightening a standard necessary condition which asserts that such directions must be minimal support solutions of the homogenous equation Ax = 0 which are feasible at the given vertex. We specialize the characterization for polyhedra that correspond to network flows, obtaining a graph characterization of circuits which correspond to edge-directions. Applications to partitioning polyhedra are discussed.