Non-birationality conjecture for hyperplane restrictions of maps from very general hypersurfaces

Let Xd\bsubseteqPn+1X_d\bsubseteq \mathbb{P}^{n+1} be a very general hypersurface of degree dn+3d\geq n+3, and let YY be a smooth projective nn-fold that is non-uniruled. Let Hd:=XdHH_d:=X_d\cap H, where HH is a very general hyperplane of Pn+1\mathbb{P}^{n+1}. Suppose there is a dominant rational map f:XdYf:X_d\dashrightarrow Y with degf>1\operatorname{deg} f>1. Hyperplane-restriction conjecture. Then the restriction fHdf|_{H_d} cannot be birational to its image.

This conjecture is proposed as an inductive step toward the rational connectedness conjecture: restricting to a very general hyperplane should retain non-birationality when the target is non-uniruled. Its resolution status is not specified in the supplied text.

Sources & referencesView supporting material

Primary source

Yongnam Lee, Yujie Luo and De-Qi Zhang, “Morphisms from a very general hypersurface”, arXiv:1908.06894 (2025).

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