Hall–Rado criterion for positive products of movable classes

Let XX be a compact Kähler manifold of dimension nn, and let L1,,LkL_1,\ldots,L_k be movable classes, where 1kn1\leq k\leq n. For I[k]I\subseteq [k], write LI=iILiL_I=\sum_{i\in I}L_i, and let nd\operatorname{nd} denote numerical dimension. Hall–Rado conjecture for movable classes.

L1Lk0nd(LI)Ifor all I[k].\left\langle L_1\cdot\ldots\cdot L_k\right\rangle\neq 0 \quad\Longleftrightarrow\quad \operatorname{nd}(L_I)\geq |I|\quad\text{for all }I\subseteq [k].

This conjecturally extends the Hall–Rado positivity criterion from collections with nefness assumptions to arbitrary movable collections, replacing the ordinary intersection product by the positive product.

Sources & referencesView supporting material

Primary source

Jiajun Hu and Jian Xiao, “Positivity in the shadow of Hodge index theorem”, arXiv:2505.06626 (2025).

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