Liu–Xu's triangulation conjecture for special valuation spaces

Let (X,D)(X,D) be a klt Fano pair and let ΔQ(KX+D)\Delta\sim_{\mathbb{Q}}-(K_X+D) be a Q\mathbb{Q}-complement of (X,D)(X,D). Let D(X,D+Δ)\mathcal{D}(X,D+\Delta) be the dual complex of (X,D+Δ)(X,D+\Delta), and let DKV(X,D+Δ)\mathcal{D}^{KV}(X,D+\Delta) denote the subspace defined in the preceding question, consisting of quasi-monomial valuations up to scaling satisfying the finite-generation and klt Fano conditions there.

Liu–Xu's triangulation conjecture. There is a rational triangulation of DKV(X,D+Δ)\mathcal{D}^{KV}(X,D+\Delta) such that, in the interior of DKV(X,D+Δ)\mathcal{D}^{KV}(X,D+\Delta), the triangulation is locally finite. If CC^{\circ} is an open simplex of this triangulation, then every valuation up to scaling in CC^{\circ} induces a Gm\mathbb{G}_m-equivariant degeneration of XX into a klt Fano variety, and any two valuations in CC^{\circ} induce isomorphic Gm\mathbb{G}_m-equivariant degenerations.

This conjecture describes the global structure of the space of special valuations and asserts that valuations in a common simplex determine the same equivariant degeneration. The analogous local valuation spaces were studied previously, but the stated global triangulation and degeneration properties remain open.

Sources & referencesView supporting material

Primary source

Junyao Peng, “G_m-Equivariant Degenerations of del Pezzo Surfaces”, arXiv:2503.06612 (2025).

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