Three counter-examples on semi-graphoids

  • Authors:
  • Raymond Hemmecke;Jason Morton;Anne Shiu;Bernd Sturmfels;Oliver Wienand

  • Affiliations:
  • Fakultät für mathematik, otto-von-guericke-universität magdeburg, 39106 magdeburg, germany (e-mail: hemmecke@imo.math.uni-magdeburg.de);Department of mathematics, university of california, berkeley, ca 94720, usa (e-mail: mortonj@math.berkeley.edu, annejls@math.berkeley.edu, bernd@math.berkeley.edu);Department of mathematics, university of california, berkeley, ca 94720, usa (e-mail: mortonj@math.berkeley.edu, annejls@math.berkeley.edu, bernd@math.berkeley.edu);Department of mathematics, university of california, berkeley, ca 94720, usa (e-mail: mortonj@math.berkeley.edu, annejls@math.berkeley.edu, bernd@math.berkeley.edu);Fachbereich mathematik, technische universität kaiserslautern, 67653 kaiserslautern, germany (e-mail: wienand@mathematik.uni-kl.de)

  • Venue:
  • Combinatorics, Probability and Computing
  • Year:
  • 2008

Quantified Score

Hi-index 0.00

Visualization

Abstract

Semi-graphoids are combinatorial structures that arise in statistical learning theory. They are equivalent to convex rank tests and to polyhedral fans that coarsen the reflection arrangement of the symmetric group Sn. In this paper we resolve two problems on semi-graphoids posed in Studený's book (2005), and we answer a related question of Postnikov, Reiner and Williams on generalized permutohedra. We also study the semigroup and the toric ideal associated with semi-graphoids.