Upper Bounds for low moments of twisted Fourier coefficients of modular forms

Fuente: arXiv
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Main Authors: Gao, Peng, Wu, Xiaosheng
Format: Preprint
Published: 2025
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author Gao, Peng
Wu, Xiaosheng
author_facet Gao, Peng
Wu, Xiaosheng
contents For any large prime $q$, $1 \leq x \leq q$ and any real $0 \leq k \leq 1$, we prove an upper bound for the following $2k$-th moment $$\displaystyle \sum_{\substack{χ\bmod q}} \Big| \sum_{n\leq x} χ(n)λ(n)\Big|^{2k},$$ where $λ(n)$ denotes the Fourier coefficients of a fixed modular form. In particular, our result implies that $$\displaystyle \frac 1{q-1}\sum_{\substack{χ\bmod q}} \Big| \sum_{n\leq x} χ(n)λ(n)\Big|= o(\sqrt{x}),$$ when both $x$ and $q/x$ tend to infinity with $q$.
format Preprint
id arxiv_https___arxiv_org_abs_2512_05378
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Upper Bounds for low moments of twisted Fourier coefficients of modular forms
Gao, Peng
Wu, Xiaosheng
Number Theory
For any large prime $q$, $1 \leq x \leq q$ and any real $0 \leq k \leq 1$, we prove an upper bound for the following $2k$-th moment $$\displaystyle \sum_{\substack{χ\bmod q}} \Big| \sum_{n\leq x} χ(n)λ(n)\Big|^{2k},$$ where $λ(n)$ denotes the Fourier coefficients of a fixed modular form. In particular, our result implies that $$\displaystyle \frac 1{q-1}\sum_{\substack{χ\bmod q}} \Big| \sum_{n\leq x} χ(n)λ(n)\Big|= o(\sqrt{x}),$$ when both $x$ and $q/x$ tend to infinity with $q$.
title Upper Bounds for low moments of twisted Fourier coefficients of modular forms
topic Number Theory
url https://arxiv.org/abs/2512.05378