The isometries of the cut, metric and hypermetric cones

  • Authors:
  • Antoine Deza;Boris Goldengorin;Dmitrii V. Pasechnik

  • Affiliations:
  • Dept. of Computing and Software, McMaster University, Hamilton, Canada L8S 4K1;Aff2 Aff3;School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 639798

  • Venue:
  • Journal of Algebraic Combinatorics: An International Journal
  • Year:
  • 2006

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Abstract

We show that the symmetry groups of the cut cone Cutn and the metric cone Metn both consist of the isometries induced by the permutations on $$\{1,\dots,n\}$$ , that is, $$Is(\mathrm{Cut}{n})=Is(\mathrm{Met}{n})\simeq Sym{n}$$ for n 驴 5. For n = 4 we have $$Is(\mathrm{Cut}{4})=Is(\mathrm{Met}{4})\simeq Sym{3}\times Sym{4}$$ . This result can be extended to cones containing the cuts as extreme rays and for which the triangle inequalities are facet-inducing. For instance, $$ Is ({\rm Hyp}_n) \simeq Sym(n)$$ for n 驴 5, where Hypn denotes the hypermetric cone.