Takagi's log canonicity and dense sharp F-purity conjecture

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Let XX be a normal variety over an algebraically closed field KK of characteristic zero, and let DD be an effective Q\mathbb{Q}-divisor on XX such that KX+DK_X+D is Q\mathbb{Q}-Cartier. Let Z=∑itiZiZ=\sum_i t_i Z_i be a formal combination, where the tit_i are nonnegative rational numbers and the ZiZ_i are proper closed subschemes of XX. Fix a point x∈Xx\in X. Log canonicity–dense sharp FF-purity conjecture.

  1. ((X,D);Z)((X,D);Z) is log canonical at xx if and only if it is of dense sharply FF-pure type at xx.
  2. If (X,D)(X,D) is log canonical at xx, then for any model of (X,D,Z,x)(X,D,Z,x) over a finitely generated Z\mathbb{Z}-subalgebra BB of KK, there is a dense subset of closed points W⊆Spec⁡BW\subseteq\operatorname{Spec}B such that
lct⁡x((X,D);Z)=fpt⁡xμ((Xμ,Dμ);Zμ)\operatorname{lct}_x((X,D);Z)=\operatorname{fpt}_{x_\mu}((X_\mu,D_\mu);Z_\mu)

for every μ∈W\mu\in W. The conjecture proposes an arithmetic correspondence between log canonicity and sharp FF-purity, extending the known correspondence between klt singularities and strongly FF-regular type. The source describes this correspondence as largely conjectural and does not state a resolution.

References

Primary source

Shunsuke Takagi, “Adjoint ideals and a correspondence between log canonicity and F-purity”, arXiv:1105.0072 (2013).

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