Rank one elliptic curves and rank stability

For any quadratic extension $L\mathrm{/}K$ of number fields, we prove that there are infinitely many elliptic curves $E$ over $K$ so that the abelian groups $E(K)$ and $E(L)$ both have rank $1$. In particular, there are infinitely many elliptic curves of rank $1$ over any number field. This result generalizes theorems of Koymans-Pagano and Alpöge-Bhargava-Ho-Shnidman which were used to independently show that Hilbert’s tenth problem over the ring of integers of any number field has a negative answer. Our approach differs since we are obtaining our elliptic curves by specializing a nonisotrivial rank $1$ family of elliptic curves and we compute all the ranks involved.