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The isometries of the cut, metric and hypermetric cones
Authors:Antoine Deza  Boris Goldengorin  Dmitrii V. Pasechnik
Affiliation:(1) Dept. of Computing and Software, McMaster University, Hamilton, Ontario, Canada, L8S 4K1;(2) Dept. of Econometrics and Operations Research, University of Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands;(3) Dept. of Applied Mathematics, Khmelnitsky National University, Ukraine;(4) School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798
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 ≥ 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 ≥ 5, where Hypn denotes the hypermetric cone.
Keywords:Polyhedral combinatorics  Metric cone  Hypermetric cone  Symmetry group
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