Quadratic Chabauty Experiments on Genus 2 Bielliptic Modular Curves in the LMFDB

Abstract

We present results of quadratic Chabauty experiments on genus 2 bielliptic modular curves of Jacobian rank 2 that have recently been added to the LMFDB. We apply quadratic Chabauty methods over both the rationals and quadratic imaginary fields. In a number of cases, the experiments yielded algebraic irrational points among the set of mock rational points. We highlight specific notable examples, including the non-split Cartan modular curve $X_{ns}^{+}(15)$. Lastly, we offer a conjecture relating the level of the modular curve to the potential number fields over which points can arise.

17 pages, accepted to LuCaNT 2025 conference proceedings. Version 2 addresses referee comments