Stapledon's equivalence conjecture for equivariant H*-series

Let GG be a finite group acting on a lattice, and let PP be a GG-invariant lattice polytope. Let YY be the toric variety with ample line bundle LL associated to PP, and let H[t]H^*[t] denote the equivariant HH^*-series of PP. Stapledon's equivalence conjecture. The following conditions are equivalent: LL admits a GG-invariant section defining a non-degenerate hypersurface of YY; H[t]H^*[t] is effective; and H[t]H^*[t] is a polynomial.

The implications from the first condition to the second and from the second to the third are known, but counterexamples show that neither the second nor the third condition implies the first. Thus the stated equivalence is refuted.

Sources & referencesView supporting material

Primary source

Oliver Clarke, Akihiro Higashitani and Max Kölbl, “The equivariant Ehrhart theory of polytopes with order-two symmetries”, arXiv:2209.00755 (2023).

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