Moments of L-functions attached to the twist of modular form by Dirichlet characters

Abstract

Let f(z) be a holomorphic cusp form of weight κ with respect to the full modular group SL ₂(ℤ). Let L(s, f) be the automorphic L-function associated with f(z) and χ be a Dirichlet character modulo q. In this paper, the authors prove that unconditionally for $k = \tfrac{1}{n}$ with n ∈ ℕ, $M_k \left( {q,f} \right) = \sum\limits_{\begin{array}{*{20}c} {\chi (\bmod q)} \\ {\chi \ne \chi _0 } \\ \end{array} } {\left| {L\left( {\frac{1}{2},f \otimes \chi } \right)} \right|^{2k} < < _k \varphi \left( q \right)(\log q)^{k^2 } ,}$ and the result also holds for any real number 0 < k < 1 under the GRH for L(s, f ⊗ χ). The authors also prove that under the GRH for L(s, f ⊗ χ), $M_k \left( {q,f} \right) > > _k \varphi (q)(log q)^{k^2 }$ for any real number k > 0 and any large prime q.

Keywords

Moments / Automorphic L-functions / Convexity theorem

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