ON THE GROWTH OF TATE–SHAFAREVICH GROUPS OF $\boldsymbol {p}$-SUPERSINGULAR ABELIAN VARIETIES OF $\textbf {GL}_{\textbf {2}}$-TYPE OVER $\boldsymbol {\mathbb {Z}}_{\boldsymbol {p}}$-EXTENSIONS OF NUMBER FIELDS

Abstract We study the boundedness of the Mordell–Weil rank and the growth of the v -primary part of the Tate–Shafarevich group of p -supersingular abelian varieties of $\mathrm {GL}_2$ -type with real multiplication over $\mathbb Z_p$ -extensions of number fields, where v is a prime lying above p . Building on the work of Iovita and Pollack in the case of elliptic curves, under precise ramification and splitting conditions on p , we construct explicit systems of local points using the theory of Lubin–Tate formal groups. We then define signed Coleman maps, which in turn allow us to formulate and analyse signed Selmer groups. Assuming these Selmer groups are cotorsion, we prove that the Mordell–Weil groups are bounded over any subextensions of the ${\mathbb Z}_p$ -extension and provide an asymptotic formula for the growth of the v -primary part of the Tate–Shafarevich groups. Our results extend those of Kobayashi, Pollack, and Sprung on p -supersingular elliptic curves.