Ambro–Ionescu–Kawamata effective adjunction conjecture

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Let (X,L)(X,L) be a projective variety of dimension nn with at most terminal Q\mathbb{Q}-factorial singularities, where LL is a nef and big Cartier divisor; such a pair (X,L)(X,L) is called a quasi polarized pair. Let t>0t>0. Effective adjunction conjecture. If

KX+tL∈Eff⁡(X)‾,K_X+tL\in\overline{\operatorname{Eff}(X)},

then

H0(X,KX+tL)≠0.H^0(X,K_X+tL)\neq 0.

This is an effective strengthening of the preceding nonvanishing proposition. The case t=1t=1 is a version of the Ambro–Ionescu–Kawamata conjecture, known for n≤3n\leq 3; the case t=n−1t=n-1 recovers a conjecture of Beltrametti and Sommese.

References

Primary source

Marco Andreatta and Claudio Fontanari, “Effective Adjunction Theory”, arXiv:1703.00758 (2018).

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