Liu–Xu's triangulation conjecture for special valuation spaces

Let (X,D)(X,D) be a klt Fano pair and let Δ∼Q−(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 C∘C^{\circ} is an open simplex of this triangulation, then every valuation up to scaling in C∘C^{\circ} induces a Gm\mathbb{G}_m-equivariant degeneration of XX into a klt Fano variety, and any two valuations in C∘C^{\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.

References

Primary source

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

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