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γ-positivity for duals of symmetric edge polytopes

The h*-polynomials of symmetric edge polytopes are not always γ-positive (counterexample, 2026). What about their polar duals, a class of alcoved polytopes?

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@misc{cairn-alcoved-polytopes-gamma-positivity,
  title        = {γ-positivity for duals of symmetric edge polytopes},
  author       = {{Cairn Commons contributors}},
  howpublished = {\url{https://cairn-commons.com/problems/alcoved-polytopes-gamma-positivity}},
  year         = {2026},
  note         = {Open problem on Cairn Commons, CC BY-SA 4.0. Accessed 2026-10-04}
}

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The problem

The question

Symmetric edge polytopes of graphs are reflexive lattice polytopes; their polar duals form a subclass of alcoved polytopes. Study the Ehrhart theory of these duals; in particular, are their h*-polynomials γ-positive? (A palindromic polynomial h(x) of degree d is γ-positive if h(x) = Σ γ_i x^i (1 + x)^{d − 2i} with all γ_i ≥ 0.)

What is known

The Ohsugi–Tsuchiya conjecture that h*-polynomials of symmetric edge polytopes themselves are γ-positive was disproved in 2026 with series-parallel counterexamples. The question for the polar duals is open.

What counts as progress

  • Computation of h*-polynomials and γ-vectors of the duals for all graphs up to a given size (Normaliz, LattE), with code and data.
  • A counterexample: one graph whose dual polytope has a negative γ_i — an exact, checkable computation.
  • Proofs for graph families.

How it is checked

h*-vectors are exact integer computations; a negative γ_i is a certificate reproducible by independent software (level B).

Source. Posed by the participants of the mini-workshop (working-group problem) in the open problem session of the Oberwolfach workshop Mini-Workshop: Alcoved Polytopes in Physics and Optimization (2025), recorded in Oberwolfach Reports 12/2025, p. 532 (EMS Press, DOI 10.4171/OWR/2025/12), licensed under CC BY-SA 4.0. This page summarises the problem in our own words; as an adaptation it is shared under CC BY-SA 4.0 as well.