The −1-1-curves conjecture for blowups of the projective plane

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Let S=SnS=S_n be the blowup of the projective plane at nn very general points. Let NR1(S)N^1_{\mathbb R}(S) be the real Néron–Severi space, let NE⁡‾(S)\overline{\operatorname{NE}}(S) be the Mori cone, and let L\mathscr L denote the light cone. A −1-1-curve is a curve c⊂Sc\subset S isomorphic to P1\mathbb P^1 with c2=−1c^2=-1.

−1-1-curves conjecture. The Mori cone of SS is generated by the light cone and the −1-1-curves. Dually,

Nef⁡(S)={v∈L∣v⋅c≥0 for every −1-curve c⊂S}.\operatorname{Nef}(S)=\{v\in\mathscr L\mid v\cdot c\ge 0\text{ for every }-1\text{-curve }c\subset S\}.

This conjecture concerns the geometry of the Mori and nef cones for blowups at very general points, particularly when n>9n>9, where these cones are not completely understood. The source attributes it to Tommaso de Fernex and cites an erratum, but gives no resolution status.

References

Primary source

Luíze D'Urso, “On the Nef cones of blowups of the projective plane”, arXiv:2412.15460 (2025).

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