Strictness conjecture for inclusions of BPF and nef b-divisor spaces

Let XX be a projective manifold of dimension at least 22, and let X\mathcal{X} be its Riemann–Zariski space. Consider the continuous injections

NBPF1(X)Vect(Nef1(X))NΣ1(X)Nω1(X)=NBPF1,(X)w-N1(X).\operatorname{N}_{\operatorname{BPF}}^{1}(\mathcal{X})\hookrightarrow \operatorname{Vect}(\operatorname{Nef^1}(\mathcal{X}))\hookrightarrow \operatorname{N^1_{\Sigma}}(\mathcal{X})\hookrightarrow \operatorname{N}^1_{\omega}(\mathcal{X})=\operatorname{N}^{1,\vee}_{\operatorname{BPF}}(\mathcal{X})\hookrightarrow \operatorname{w-N}^1(\mathcal{X}).

Strictness conjecture. All the inclusions in this sequence are strict.

These inclusions compare several Banach and completed spaces of bb-divisor classes used in the study of degree growth of rational self-maps. The first and last injections were previously known, while the equality and the two intermediate injections are established in the source; the strictness assertion remains open.

Sources & referencesView supporting material

Primary source

Nguyen-Bac Dang and Charles Favre, “Intersection theory of nef b-divisor classes”, arXiv:2007.04549 (2021).

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