Kollár's canonical model conjecture after a base change

Let g:XΔg:\mathcal X\to\Delta be a flat, proper, Moishezon morphism, where Δ\Delta is the unit disc in C\mathbb C. Assume that X0X_0 has only canonical singularities. A morphism ν:Δ~Δ\nu:\widetilde\Delta\to\Delta is surjective if it is onto, and let g~\widetilde g denote the base change of gg induced by ν\nu. Kollár's base-change canonical model conjecture. After shrinking Δ\Delta, there exists a surjective morphism ν:Δ~Δ\nu:\widetilde\Delta\to\Delta with τν1(0)\tau\in\nu^{-1}(0) such that g~\widetilde g is fiberwise bimeromorphic, possibly after shrinking Δ~\widetilde\Delta, to a flat, projective morphism

gp:XpΔ~g^{\mathrm p}:\mathcal X^{\mathrm p}\to\widetilde\Delta

whose fiber over τ\tau has only canonical singularities, whose fibers over sτs\ne\tau have terminal singularities, and for which KXPK_{\mathcal X^{\mathrm P}} is Q\mathbb Q-Cartier. This is proposed as a possible approach to Kollár's canonical-case conjecture; the supplied text gives no resolution.

Sources & referencesView supporting material

Primary source

Jian Chen, Sheng Rao and I-Hsun Tsai, “Characterization of fiberwise bimeromorphism and specialization of bimeromorphic types I: locally Moishezon case”, arXiv:2506.12670 (2026).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.