Generalized Ambro conjecture for weak log Fano pairs

Let (Y,B)(Y,B) be an ϵ\epsilon-klt weak log Fano pair of dimension nn with YY having at worst terminal singularities. For a Q\mathbb{Q}-Cartier divisor GG satisfying G+B0G+B\geq0, define

glct(Y,B;G)=sup{t[0,1]Q(Y,B+tG) is lc}.{\rm glct}(Y,B;G)=\sup\{t\in[0,1]\cap\mathbb{Q}\mid (Y,B+tG)\text{ is lc}\}.

Generalized Ambro conjecture. Fix 0<ϵ<10<\epsilon<1 and an integer n>0n>0. Then there exists a number μ(n,ϵ)>0\mu(n,\epsilon)>0 depending only on nn and ϵ\epsilon such that

inf{glct(Y,B;G)GQ(KY+B), G+B0}μ(n,ϵ).\inf\{ {\rm glct}(Y,B;G)\mid G\sim_\mathbb{Q}-(K_Y+B),\ G+B\geq0\}\geq\mu(n,\epsilon).

This stronger formulation allows GG to be non-effective, subject to G+B0G+B\geq0, and is needed for the paper's argument. The supplied text gives no resolution status, so it is recorded as open with low confidence.

Sources & referencesView supporting material

Primary source

Chen Jiang, “Boundedness of anti-canonical volumes of singular log Fano threefolds”, arXiv:1411.6728 (2017).

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