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Let $\rho(f):G_\mathbb{Q} \rightarrow GL_2(K_f)$ be the Galois representation attached to some cuspidal modular form $f$ where $K_f$ is a finite extension of $\mathbb{Q}_p$. Let $V_f$ be the vector space of this representation with Tate module $T_f$. Denote $A_f=V_f/T_f$. Let $S$ be the set of ramified primes for the representation (primes dividing p and the level of the modular form). Let $S$ also contain the infinite primes. Let $\mathbb{Q}_S$ be the maximal extension of $\mathbb{Q}$ unramified outside $S$.

I would like to know if the following two modules are finite:

  1. $H^0(\mathbb{Q}_S/\mathbb{Q}(\mu_{p^\infty}),A_{f})$

  2. ${\oplus_{v \in S}H^0(\mathbb{Q}(\mu_{p^\infty})_v,A_{f})}$

Here $\mathbb{Q}(\mu_{p^\infty})_v$ is the completion of $\mathbb{Q}(\mu_{p^\infty})$ at prime $v$.

I won't mind if someone gives me references for the cyclotomic $\mathbb{Z}_p$extension of $\mathbb{Q}$ instead of $\mathbb{Q}(\mu_{p^\infty})$.

I know that these results are true for elliptic curves (with good reduction at $p$) and abelian varieties (results of Imiai and Ribet).

I know that both the statements are true for cuspidal modular forms with good ordinary reduction at $p$.

I know that for $v=p$, (2) is true for cuspidal modular forms with supersingular reduction at $p$ with $a_p(f)=0$.

I don't know the references for the other cases. Is there a unified proof of these "classical" facts for all cuspidal modular forms somewhere in the literature? I will be grateful if someone gives me references of these results for all cuspidal modular forms.

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  • $\begingroup$ (1) is true for any $f$ and is an easy consequence of Momose and Ribet's results on big Galois image. Are you sure (2) is true for elliptic curves? Looks to me like it should be false if $p \in S$ and $E$ has split multiplicative reduction at $p$. $\endgroup$ Commented Nov 3, 2020 at 9:28
  • $\begingroup$ @David, What is the reference for Momose and Ribet's results on big Galois image? I think you are right; $E$ should have good reduction at $p$. For what all modular forms is (2) true in general? $\endgroup$
    – user100603
    Commented Nov 3, 2020 at 14:28
  • $\begingroup$ See Ribet's paper dx.doi.org/10.1017/S0017089500006170. $\endgroup$ Commented Nov 3, 2020 at 16:58
  • $\begingroup$ @David. Thanks for the link. $\endgroup$
    – user100603
    Commented Nov 6, 2020 at 16:45

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