Campana's conjecture over function fields

Let XX be a smooth projective variety over \a9C\a9\mathbb{C} and let DD be a strict normal crossings divisor on XX with irreducible components D1,,DqD_1,\ldots,D_q. For each 1jq1\leq j\leq q, let \a9ϵj>0\a9\epsilon_j>0 be rational and set ϵ=(ϵ1,,ϵq)\overline{\epsilon}=(\epsilon_1,\ldots,\epsilon_q) and Dϵ=j=1qϵjDjD_{\overline{\epsilon}}=\sum_{j=1}^q\epsilon_jD_j. Let KXK_X be a canonical divisor, let CC be an (X,Dϵ)(X,D_{\overline{\epsilon}})-Campana curve with normalization νC:C~X\nu_C:\widetilde C\to X, let g(C)g(C) denote the genus of C~\widetilde C, and let hA(νC)h_{\mathcal A}(\nu_C) be the height associated with an ample sheaf A\mathcal A. If

KX+(DDϵ)K_X+(D-D_{\overline{\epsilon}})

is big, then Campana's conjecture. There exist a proper Zariski closed subset Zϵ,ω,DXZ_{\overline{\epsilon},\omega,D}\subseteq X, an ample sheaf A\mathcal A on XX, and a constant BB depending on the preceding data, in particular on ϵ\overline{\epsilon} and DD, such that every (X,Dϵ)(X,D_{\overline{\epsilon}})-Campana curve CXC\subseteq X not contained in Zϵ,ω,DZ_{\overline{\epsilon},\omega,D} satisfies

hA(νC)Bmax{0,g(C)1}.h_{\mathcal A}(\nu_C)\leq B\max\{0,g(C)-1\}.

This is the function-field form of Campana's conjecture, predicting height control—and hence algebraic degeneracy outside a proper exceptional set—for Campana curves when the orbifold canonical divisor is big. The source presents it as a conjectural statement and refers to the analogous number-field formulation and to existing partial results, so its resolution status is not established here.

Sources & referencesView supporting material

Primary source

Natalia Garcia-Fritz, “On the conjectures of Vojta and Campana over function fields with explicit exceptional sets”, arXiv:2203.00626 (2022).

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