The strong and weak Gamma-effective adjunction conjectures

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Let (X,D)(X,D) be an klt (respectively, lc) pair with dimension dd, and let f:(X,D)Zf:(X,D)\to Z be an lc-trivial fibration. An R\mathbb R-b-divisor M{\bf M} is Γ\Gamma-base-point free if it is a convex combination of base-point free b-divisors with coefficients in a finite set Γ(0,1]\Gamma\subset(0,1]. Let D\mo{\bf D}_{\mo} denote the moduli b-divisor. Strong and weak Γ\Gamma-effective adjunction conjectures. (1) If the coefficients of the horizontal divisors of DD belong to a finite set IhI_h, then there exist a finite set Γ(0,1]\Gamma\subset(0,1] and a positive integer mm, depending only on dd and IhI_h, such that mD\mom{\bf D}_{\mo} is Γ\Gamma-base-point free. (2) If the coefficients of DD belong to a DCC set I(0,1]I\subset(0,1], then there exist a DCC set J(0,1]J\subset(0,1], a finite set Γ(0,1]\Gamma\subset(0,1], and a positive integer mm, all depending only on dd and II, together with b-divisors D~\di\widetilde{\bf D}_{\di} and D~\mo\widetilde{\bf D}_{\mo} satisfying: (D~\di)ZJ(\widetilde{\bf D}_{\di})_Z\in J; mD~\mom\widetilde{\bf D}_{\mo} is Γ\Gamma-base-point free; (Z,D~\di)(Z,\widetilde{\bf D}_{\di}) is klt (respectively, lc); and for birational morphisms p:ZZp:Z'\to Z, q:XXq:X'\to X and a morphism f:XZf':X'\to Z' with fq=pff\circ q=p\circ f', one has

q(KX+D)Rf(KZ+(D~\di)Z+(D~\mo)Z).q^*(K_X+D)\sim_{\mathbb R}f'^*(K_{Z'}+(\widetilde{\bf D}_{\di})_{Z'}+(\widetilde{\bf D}_{\mo})_{Z'}).

This variant is proposed to make effective adjunction compatible with inductions and real coefficients. Its status is open in the supplied source.

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Sources & referencesView supporting material

Primary source

Zhan Li, “A variant of the effective adjunction conjecture with applications”, arXiv:2007.04107 (2020).

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