Quasi--splitting of general fibers with trivial relative canonical divisor
Let be a fiber space of normal varieties. The relative canonical divisor is trivial if is linearly equivalent to zero, and is quasi--split when it satisfies the quasi--splitting condition defined in the paper.
General-fiber quasi--splitting conjecture. If the relative canonical divisor is trivial and is quasi--split, then a general fiber of is quasi--split.
The assumption that the generic fiber is a complete intersection in the preceding corollary is technical, motivating this conjecture. It is disproved in general when the relative canonical divisor is anti-ample, as shown by the paper's wild conic bundle example; the stated trivial-divisor case is therefore not supported as an open conjecture by the supplied status evidence.
References
Primary source
Tatsuro Kawakami, Teppei Takamatsu and Shou Yoshikawa, “Fedder type criteria for quasi-F-splitting I”, arXiv:2204.10076 (2025).
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