Lefschetz decomposition conjecture for the congruence of lines and Peskine variety

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Let A\mathsf{A} be the K3 category of the Debarre–Voisin hyperplane section YY, and let TT and PP be the associated congruence of lines and Peskine variety. Let U\mathcal{U} and Q\mathcal{Q} denote the bundles used in the construction, and write (1)(1) for tensoring with the relevant polarization. Improved Lefschetz decomposition conjecture. There should be a fully faithful functor Φ:A→D⁡b(T)\Phi:\mathsf{A}\to\operatorname{D}^b(T) such that

B=⟨Φ(A),O,U∗,S2U∗⟩⊂D⁡b(T)\mathsf{B}=\langle\Phi(\mathsf{A}),\mathcal{O},\mathcal{U}^*,S^2\mathcal{U}^*\rangle\subset\operatorname{D}^b(T)

provides

D⁡b(T)=⟨B,B(1),B(2)⟩.\operatorname{D}^b(T)=\langle\mathsf{B},\mathsf{B}(1),\mathsf{B}(2)\rangle.

There should also be a fully faithful functor Ψ:A→D⁡b(P)\Psi:\mathsf{A}\to\operatorname{D}^b(P) such that

C1=⟨Ψ(A),O⟩⊂C0=⟨Ψ(A),O,Q⟩⊂D⁡b(P)\mathsf{C}_1=\langle\Psi(\mathsf{A}),\mathcal{O}\rangle\subset\mathsf{C}_0=\langle\Psi(\mathsf{A}),\mathcal{O},\mathcal{Q}\rangle\subset\operatorname{D}^b(P)

provides

D⁡b(P)=⟨C0,C1(1),C1(2)⟩.\operatorname{D}^b(P)=\langle\mathsf{C}_0,\mathsf{C}_1(1),\mathsf{C}_1(2)\rangle.

These decompositions refine the expected three-copy K3 structures and use the exceptional collections constructed for TT and PP; the source gives no proof.

References

Primary source

Marcello Bernardara, Enrico Fatighenti and Laurent Manivel, “Nested varieties of K3 type”, arXiv:1912.03144 (2019).

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