Local-global principle for 11-isogenies of elliptic curves is true over quadratic fields

Abstract

In this paper, we prove that the local-global principle of $11$-isogenies for elliptic curves over quadratic fields does not fail. This gives a positive answer to a conjecture by Banwait and Cremona. The proof is based on the determination of the set of quadratic points on the modular curve $X_{D_{10}}(11)$.

9 pages; Title has changed; We have added referees' comments;