The nef-cone conjecture for codimension-two classes on the compactification of A_3

Let A3\overline{{\mathcal A}_{3}} be the toroidal compactification, and let LL, MM, and β2\beta_2 be the classes used in the paper. Define

F1=72L2+12LM+3M2+β2,F2=72L28LM+M2β2.F_1=-72L^2+12LM+3M^2+\beta_2,\qquad F_2=72L^2-8LM+M^2-\beta_2.

Nef-cone conjecture. The cone of nef codimension-two classes is

Nef2(A3)=R0L2+R0LM+R0M2+R0F1+R0F2.\operatorname{Nef}^{2}(\overline{{\mathcal A}_{3}})={\mathbb R}_{\ge 0}L^2+{\mathbb R}_{\ge 0}LM+{\mathbb R}_{\ge 0}M^2+{\mathbb R}_{\ge 0}F_1+{\mathbb R}_{\ge 0}F_2.

The source states that this is equivalent to the main effective-cone conjecture; it remains unresolved because generation of the pseudoeffective cone by the five surfaces has not been proved.

Sources & referencesView supporting material

Primary source

Samuel Grushevsky and Klaus Hulek, “On the cone of effective surfaces on A_3”, arXiv:2007.02995 (2022).

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