Tag Archives: Weight one forms

A non-liftable weight one form modulo p^2

I once idly asked RLT (around 2004ish) whether one could use Buzzard-Taylor arguments to prove that any representation: which was unramified at p and residually irreducible (and modular) was itself modular (in the Katz sense). Galois representations of this flavour … Continue reading

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There are non-liftable weight one forms modulo p for any p

Let be any prime. In this post, we show that there is an integer prime to such that has a torsion class of order . Almost equivalently, there exists a Katz modular form of level and weight one over which … Continue reading

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