Shokurov's effective moduli-part conjecture for Fano type fibrations

Let f ⁣:XYf\colon X\to Y be a proper surjective morphism with connected fibers between normal varieties, with X/YX/Y of relative Fano type. Let Δ\Delta be a Q\mathbb Q-divisor on XX such that

KX+Δ=fLK_X+\Delta=f^*L

for some Q\mathbb Q-divisor LL on YY. Write

KX+Δ=f(KY+R+B),K_X+\Delta=f^*(K_Y+R+B),

where RR is the discriminant part and BB is the moduli part.

Shokurov's conjecture. If (X,Δ)(X,\Delta) is ϵ\epsilon-log terminal, then there exists δ=δm,n(ϵ)>0\delta=\delta_{m,n}(\epsilon)>0 and an effective moduli part BB such that (Y,R+B)(Y,R+B) is δ\delta-log terminal.

This is a stronger refinement of the epsilon-delta conjecture, incorporating the discriminant and moduli parts supplied by subadjunction. Its resolution status is not specified in the supplied text.

Sources & referencesView supporting material

Primary source

Valery Alexeev and Alexander Borisov, “On the Log Discrepancies in Toric Mori Contractions”, arXiv:1208.3271 (2013).

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