Semiampleness conjecture for the generalized Hodge line bundle on KSBA spaces

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Let f ⁣:(X,Δ+ϵB)→Sf\colon (X,\Delta+\epsilon B)\to S be a family of KSBA-stable log Calabi–Yau pairs with 0<ϵ≪10<\epsilon\ll 1, where generically KX+Δ∼Q0K_X+\Delta\sim_{\mathbb Q}0 and BB is Q\mathbb Q-Cartier and ample. Let λ\lambda be the generalized Hodge Q\mathbb Q-line bundle defined by

KX/S+Δ=f∗(λ).K_{X/S}+\Delta=f^*(\lambda).

Semiampleness conjecture. The generalized Hodge line bundle λ\lambda is semiample.

The preceding discussion shows that λ\lambda is nef, because it is obtained as the leading term of the nef classes κ1(ϵ)\kappa_1(\epsilon) as ϵ→0\epsilon\to 0. The conjecture asks for the stronger semiampleness property on the relevant KSBA moduli stack or coarse moduli space.

References

Primary source

Valery Alexeev, “Kappa classes on KSBA spaces”, arXiv:2309.14842 (2023).

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