Inversion of adjunction for minimal log discrepancies on quotient singularities

Let (X,a)(X,\mathfrak{a}) be a log pair, let DD be a normal Cartier prime divisor, and let xDx\in D be a closed point. Assume that DD is not contained in the cosupport of the R\mathbb{R}-ideal sheaf a\mathfrak{a}. The minimal log discrepancies of the pair along DD and of the restricted pair on DD are defined by

mldx(X,D,aOX)andmldx(D,aOD).\operatorname{mld}_x\bigl(X,D,\mathfrak{a}\mathcal{O}_X\bigr)\quad\text{and}\quad\operatorname{mld}_x\bigl(D,\mathfrak{a}\mathcal{O}_D\bigr).

PIA conjecture. One has

mldx(X,D,aOX)=mldx(D,aOD).\operatorname{mld}_x\bigl(X,D,\mathfrak{a}\mathcal{O}_X\bigr)=\operatorname{mld}_x\bigl(D,\mathfrak{a}\mathcal{O}_D\bigr).

This is the precise inversion of adjunction assertion investigated for quotient singularities. The paper studies it in connection with the reduction of the lower semi-continuity conjecture; the supplied context does not state whether the conjecture is resolved in full generality.

Sources & referencesView supporting material

Primary source

Yusuke Nakamura and Kohsuke Shibata, “Inversion of adjunction for quotient singularities III: semi-invariant case”, arXiv:2312.05808 (2026).

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