https://research.hub.ku.edu.tr/entities/publication/3b537ec4-a777-4611-bdd5-c641502fec9d
Dihedral group, 4-Torsion on an elliptic curve, and a peculiar eigenform modulo 4
We work out a non-trivial example of lifting a so-called weak eigenform to a true, characteristic eigenform eigenform. The weak eigenform is closely related to...