Characterization of tropical hemispaces by (P,R)-decompositions

Ricardo D. Katz, Viorel Nitica, Sergey Sergeev

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2 Citations (Scopus)
148 Downloads (Pure)


We consider tropical hemispaces, defined as tropically convex sets whose complements are also tropically convex, and tropical semispaces, defined as maximal tropically convex sets not containing a given point. We introduce the concept of (P,R)-decomposition. This yields (to our knowledge) a new kind of representation of tropically convex sets extending the classical idea of representing convex sets by means of extreme points and rays. We characterize tropical hemispaces as tropically convex sets that admit a (P,R)-decomposition of certain kind. In this characterization, with each tropical hemispace we associate a matrix with coefficients in the completed tropical semifield, satisfying an extended rank-one condition. Our proof techniques are based on homogenization (lifting a convex set to a cone), and the relation between tropical hemispaces and semispaces.
Original languageEnglish
Pages (from-to)131-163
JournalLinear Algebra and its Applications
Early online date13 Nov 2013
Publication statusPublished - 1 Jan 2014


  • Tropical convexity
  • Abstract convexity
  • Max-plus algebra
  • Hemispace
  • Semispace
  • Rank-one matrix


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