Special valuations and automorphisms of affine log Calabi--Yau varieties
Abstract
Let U be an affine log Calabi--Yau variety. Although special and finitely generated valuations are defined using a log CY-Fano compactification of U, we prove that the corresponding skeleta in the dual complex are independent of this choice, and hence invariant under Aut(U). We also show that a finitely generated valuation is special if and only if it is maximal with respect to a natural partial order induced by regular functions on U. We then consider the affine log Calabi--Yau threefold obtained as the complement of the Markov cubic surface in 𝔸3. We describe the action of the three Vieta involutions on the special skeleton and relate it to the (∞,∞,∞)-triangle reflection group on the hyperbolic plane. We also show that, for every finite triangulation of the dual complex, the special skeleton fails to be locally closed on some simplex. Via the cone construction, this provides a counterexample to a conjecture of the author and Xu.
Related
- On polarizations of affine Calabi--Yau varieties
- On algebraic dynamics of birational automorphisms of Calabi-Yau manifolds and the universal Coxeter groups
- Degree growth for tame automorphisms of an affine quadric threefold
- Dynamical degrees of automorphisms on abelian varieties
- Automorphisms of toric varieties and Gale duality
BibTeX
@misc{liu2026special,
title = {{Special valuations and automorphisms of affine log Calabi--Yau varieties}},
author = {Yuchen Liu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22737},
eprint = {2609.22737},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22737},
}
RIS
TY - UNPB
TI - Special valuations and automorphisms of affine log Calabi--Yau varieties
AU - Yuchen Liu
PY - 2026
DA - 2026/09/19
PB - arXiv
DO - 10.48550/arxiv.2609.22737
UR - https://arxiv.org/abs/2609.22737
AB - Let U be an affine log Calabi--Yau variety. Although special and finitely generated valuations are defined using a log CY-Fano compactification of U, we prove that the corresponding skeleta in the dual complex are independent of this choice, and hence invariant under Aut(U). We also show that a finitely generated valuation is special if and only if it is maximal with respect to a natural partial order induced by regular functions on U. We then consider the affine log Calabi--Yau threefold obtained as the complement of the Markov cubic surface in 𝔸^3. We describe the action of the three Vieta involutions on the special skeleton and relate it to the (∞,∞,∞)-triangle reflection group on the hyperbolic plane. We also show that, for every finite triangulation of the dual complex, the special skeleton fails to be locally closed on some simplex. Via the cone construction, this provides a counterexample to a conjecture of the author and Xu.
ER -