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

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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 Z′→ZZ'\rightarrow Z, write MZ′M_{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 Z′→ZZ'\rightarrow Z such that MZ′M_{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 dim⁡Xη\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 Z′→ZZ'\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.

References

Primary source

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

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