Facet-Hamiltonian conjecture for B-permutahedra

Let PP be a polytope of dimension dd, and call each (d1)(d-1)-dimensional face a facet. A facet-Hamiltonian cycle in PP is a cycle CC in the skeleton of PP such that, for every facet FF of PP, the intersection CFC\cap F is connected and nonempty. The BB-permutahedron has as vertices all signed permutations of [n][n], and its edges join signed permutations differing either by an adjacent transposition preserving all signs or by complementing the sign of the first entry.

Facet-Hamiltonian conjecture. The BB-permutahedron of any dimension d2d\geq 2 has a facet-Hamiltonian cycle.

The cited authors prove facet-Hamiltonian cycles for several families, including permutahedra and various associahedra, and paths for some graph associahedra. The assertion for every BB-permutahedron of dimension at least 22 remains open.

Sources & referencesView supporting material

Primary source

Nastaran Behrooznia, Sofia Brenner, Arturo Merino, Torsten Mütze, Christian Rieck and Francesco Verciani, “Listing faces of polytopes”, arXiv:2412.02584 (2026).

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