Boundedness up to special degeneration from positive local volume

Let nn be a positive integer, and let ϵ,η\epsilon,\eta be positive numbers. A special degeneration of a klt singularity is the central fiber of a special test configuration as defined in the paper; a set of singularities is log bounded up to special degeneration if it admits the corresponding bounded model after such a degeneration. Let x(X,Δ)x\in(X,\Delta) be an nn-dimensional klt singularity, and let vol^(x,X,Δ)\widehat{\operatorname{vol}}(x,X,\Delta) denote its local volume. Boundedness conjecture up to special degeneration. The set of such singularities satisfying

vol^(x,X,Δ)ϵ\widehat{\operatorname{vol}}(x,X,\Delta)\geq\epsilon

and having all coefficients of Δ\Delta at least η\eta is log bounded up to special degeneration.

This conjecture would extend the known boundedness theorem for Q\mathbb{Q}-Gorenstein singularities admitting δ\delta-plt blow-ups. The paper proves the claim in several cases, but the general statement remains open.

Sources & referencesView supporting material

Primary source

Jingjun Han, Yuchen Liu and Lu Qi, “ACC for local volumes and boundedness of singularities”, arXiv:2011.06509 (2022).

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