Likely intersections

Abstract

We prove a general likely intersections theorem, a counterpart to the Zilber-Pink conjectures, under the assumption that the Ax-Schanuel property and some mild additional conditions are known to hold for a given category of complex quotient spaces definable in some fixed o-minimal expansion of the ordered field of real numbers. For an instance of our general result, consider the case of subvarieties of Shimura varieties. Let $S$ be a Shimura variety. Let $\pi:D \to \Gamma \backslash D = S$ realize $S$ as a quotient of $D$, a homogeneous space for the action of a real algebraic group $G$, by the action of $\Gamma < G$, an arithmetic subgroup. Let $S' \subseteq S$ be a special subvariety of $S$ realized as $\pi(D')$ for $D' \subseteq D$ a homogeneous space for an algebraic subgroup of $G$. Let $X \subseteq S$ be an irreducible subvariety of $S$ not contained in any proper weakly special subvariety of $S$. Assume that the intersection of $X$ with $S'$ is persistently likely meaning that whenever $\zeta:S_1 \to S$ and $\xi:S_1 \to S_2$ are maps of Shimura varieties (meaning regular maps of varieties induced by maps of the corresponding Shimura data) with $\zeta$ finite, $\dim \xi \zeta^{-1} X + \dim \xi \zeta^{-1} S' \geq \dim \xi S_1$. Then $X \cap \bigcup_{g \in G, \pi(g D') \text{ is special }} \pi(g D')$ is dense in $X$ for the Euclidean topology.