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)Z∈J(\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:Z′→Zp:Z'\to Z, q:X′→Xq:X'\to X and a morphism f′:X′→Z′f':X'\to Z' with f∘q=p∘f′f\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.

References

Primary source

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

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