Prokhorov–Shokurov's effective b-semiampleness conjecture
Fix an integer . For every lc-trivial fibration of relative dimension , choose a birational diagram
Here and are birational, and denotes the trace of the moduli b-divisor.
Effective b-semiampleness conjecture. There is an integer such that one can choose the diagram with , Cartier and free, and descending to .
This is the effective, uniform form of the b-semiampleness expectation: the index depends only on the relative dimension. The conjecture is open in the stated generality.
References
Primary source
Philip Engel, Stefano Filipazzi, François Greer, Mirko Mauri and Roberto Svaldi, “Boundedness of some fibered K-trivial varieties”, arXiv:2507.00973 (2025).
Additional references
8 papers in this index state this conjecture (2012–2025). The statement above is taken from the most recent of them; the others are arXiv:2405.05489, arXiv:2203.11460, arXiv:2111.03373, arXiv:2005.02613, arXiv:1907.10490, arXiv:1808.00717, arXiv:1207.4070.
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