Iitaka fibration conjecture for integral points on polarized log Fano varieties

Let X=(X,D,L)\mathcal{X}=(\mathfrak{X},D,L) be a polarized log Fano variety, with integral-point scheme U=XD\mathfrak{U}=\mathfrak{X}\setminus\overline{D}, height function HLH_L, and counting function

NX,Z(B)=#{xU(\mathdsZ)ZHL(x)B}.N_{\mathcal{X},Z}(B)=\#\{x\in\mathfrak{U}(\mathds{Z})\setminus Z\mid H_L(x)\leq B\}.

Assume that U(\mathdsZ)\mathfrak{U}(\mathds{Z}) is not thin. Let ϕ=ϕ(X,L) ⁣:XW\phi=\phi_{(X,L)}\colon X\dashrightarrow W be the Iitaka fibration induced by the adjoint bundle EX=KX+D+a(X)LE_{\mathcal{X}}=K_X+D+a(\mathcal{X})L. For each tW(\mathdsQ)t\in W(\mathds{Q}) for which the fiber is defined, let XtX_t and Xt\mathfrak{X}_t be its closures in XX and X\mathfrak{X}, and set Xt=(Xt,DXt,LXt)\mathcal{X}_t=(\mathfrak{X}_t,D\cap X_t,L|_{X_t}). A fiber is adjoint rigid when its adjoint bundle is rigid. Iitaka fibration conjecture. There are thin sets ZX(\mathdsQ)Z\subset X(\mathds{Q}) and YW(\mathdsQ)Y\subset W(\mathds{Q}) such that for every tW(\mathdsQ)Yt\in W(\mathds{Q})\setminus Y, the fiber Xt\mathcal{X}_t is adjoint rigid with a(Xt)=a(X)a(\mathcal{X}_t)=a(\mathcal{X}) and b(Xt)=b(X)b(\mathcal{X}_t)=b(\mathcal{X}), the sum

c(X)=tW(\mathdsQ)Yc(Xt)c(\mathcal{X})=\sum_{t\in W(\mathds{Q})\setminus Y}c(\mathcal{X}_t)

converges, and

NX,Z(B)c(X)Ba(X)(logB)b(X)1.N_{\mathcal{X},Z}(B)\sim c(\mathcal{X})B^{a(\mathcal{X})}(\log B)^{b(\mathcal{X})-1}.

This conjecture proposes that, in the non-adjoint-rigid case, the leading constant and asymptotic count decompose through the Iitaka fibration into contributions from adjoint-rigid fibers. The supplied text does not give evidence resolving the conjecture.

Sources & referencesView supporting material

Primary source

Ulrich Derenthal and Florian Wilsch, “Iitaka fibrations and integral points: a family of arbitrarily polarized spherical threefolds”, arXiv:2505.10245 (2025).

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