Prokhorov–Shokurov conjectures on the moduli part of the canonical bundle formula

Let f ⁣:(X,B)Zf\colon(X,B)\rightarrow Z be an lc-trivial fibration, and let MZM_Z denote the moduli divisor in the canonical bundle formula. For a birational model ZZZ'\rightarrow Z, write MZM_{Z'} for the corresponding birational transform of the moduli divisor.

Prokhorov–Shokurov conjectures. The following properties are conjectured:

  1. Log canonical adjunction: There exists a proper birational morphism ZZZ'\rightarrow Z such that MZM_{Z'} is semiample.
  2. Particular case of effective log abundance: If XηX_{\eta} is the generic fibre of ff, then
I0(KXη+Bη)0,I_0(K_{X_{\eta}}+B_{\eta})\sim 0,

where I0I_0 depends only on dimXη\dim X_{\eta} and the multiplicities of the horizontal part of BB. 3. Effective adjunction: There exists a positive integer II, depending only on the dimension of XX and the horizontal multiplicities of BB, such that IMZIM_Z is the pullback of a divisor MM that is base point free on some model ZZZ'\rightarrow Z.

These conjectures concern semiampleness and effective boundedness of the moduli part in the canonical bundle formula. The source presents them as conjectural properties; no resolution is supplied here.

Sources & referencesView supporting material

Primary source

Enrica Floris, “Bounds on the denominators in the canonical bundle formula”, arXiv:1105.4553 (2012).

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