Mathieu Dutour Sikirić

Mathieu Dutour Sikirić

m-Hemi-metric and m-Hemi-cut Cones

Definitions

  • m-Hemi-metric: A function d defined over (m+1)-tuples of {1,...,n} that is invariant under permutation, equals 0 if any two elements are identical, is non-negative, and satisfies the m-hemi-metric triangle inequality.
  • m-Hemi-metric Cone (HMETmn): The polyhedral cone of all m-hemi-metrics for fixed m and n.
  • m-Partition Hemi-metric: For an unordered (m+1)-partition of {1,...,n}, d = 0 if any two elements belong to the same subset, and 1 otherwise.
  • m-Hemi-cut Cone (HCUTmn): The positive span of all m-partition hemi-metrics.

Computational Results

Cones for n=5, 6

ConeDimGroupExtreme RaysFacetsDetails
HCUT2510Sym(5)25 (2 orbits)120 (4 orbits)TeX | PS
HMET2510Sym(5)37 (3 orbits)30 (2 orbits)TeX | PS
HCUT3615Sym(6)65 (2 orbits)4,065 (16 orbits)TeX | PS
HMET3615Sym(6)287 (5 orbits)45 (2 orbits)TeX | PS
HCUT2620Sym(6)90 (3 orbits)2,095,154 (3086 orbits)List
HMET2620Sym(6)12,492 (41 orbits)80 (2 orbits)TeX | PS

Cones for n=7, 8

ConeDimGroupExtreme RaysFacetsDetails
HCUT4721Sym(7)140 (2 orbits)474,390 (153 orbits)List
HMET4721Sym(7)3,692 (8 orbits)63 (2 orbits)TeX | PS
HCUT5828Sym(8)266 (2 orbits)≥ 408,276,708Incomplete
HMET5821Sym(8)55,898 (13 orbits)84 (2 orbits)List

Lower Bounds for n=7

  • HMET37: Dim 35 | ≥ 373,014,230 extreme rays (≥ 74,878 orbits) | 140 facets (2 orbits).
  • HMET27: Dim 35 | ≥ 243,895,508 extreme rays (≥ 49,715 orbits) | 175 facets (2 orbits).