Birational rigidity conjectures for codimension-two Fano threefold WCIs

Let XX be a quasismooth Fano threefold weighted complete intersection of codimension 22 and index 11, belonging to a deformation family indexed by II. Let IbrI_{br}, IFI_F, and IdPI_{dP} denote the families described in the preceding classification, and in the case of XX belonging to IFI_F, let XX' be the Fano threefold in part (2) of the cited theorem. Birational rigidity conjecture. (1) Any smooth complete intersection of a quadric and a cubic in P5\mathbb P^5 is birationally rigid. (2) Any quasismooth member XX belonging to a family indexed by IFI_F is not birational to a Mori fibre space other than XX and XX'. The first assertion concerns the remaining smooth quadric–cubic case, while the second predicts the complete list of Mori fibre spaces birational to members of the families indexed by IFI_F. The source presents these assertions as conjectural; no resolution is supplied here.

Sources & referencesView supporting material

Primary source

Tiago Duarte Guerreiro and Takuzo Okada, “A survey on birational Rigidity of threefold Weighted Complete Intersections”, arXiv:2508.13025 (2025).

Additional references

6 papers in this index state this conjecture (1999–2025). The statement above is taken from the most recent of them; the others are arXiv:2011.07512, arXiv:1712.08906, arXiv:1310.5548, arXiv:math/0410558, arXiv:math/9911210.

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