Unexpected primes of good reduction in quotients of modular and Shimura curves
arXiv:2607.11248
Abstract
We find all zero-dimensional spaces of newforms of weight and squarefree level with a fixed Atkin--Lehner sign pattern. As an application, we classify unexpected primes of good reduction of Atkin--Lehner quotients of modular and Shimura curves of squarefree levels.
18 pages. Comments welcome!