Hilbert’s tenth problem in anticyclotomic towers of number fields

Abstract:

Let $K$ be an imaginary quadratic field and $p$ be an odd prime which splits in $K$. Let $E_1$ and $E_2$ be elliptic curves over $K$ such that the $\operatorname {Gal}(\bar {K}/K)$-modules $E_1[p]$ and $E_2[p]$ are isomorphic. We show that under certain explicit additional conditions on $E_1$ and $E_2$, the anticyclotomic $\mathbb {Z}_p$-extension $K_{\operatorname {anti}}$ of $K$ is integrally diophantine over $K$. When such conditions are satisfied, we deduce new cases of Hilbert’s tenth problem. In greater detail, the conditions imply that Hilbert’s tenth problem is unsolvable for all number fields that are contained in $K_{\operatorname {anti}}$. We illustrate our results by constructing an explicit example for $p=3$ and $K=\mathbb {Q}(\sqrt {-5})$.