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Main Authors: Jenkins, Paul, Rouse, Jeremy
Format: Preprint
Published: 2025
Subjects:
Online Access:https://arxiv.org/abs/2507.17949
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author Jenkins, Paul
Rouse, Jeremy
author_facet Jenkins, Paul
Rouse, Jeremy
contents We study modular forms for $\textrm{SL}_2(\mathbb{Z})$ with no negative Fourier coefficients. Let $A(k)$ be the positive integer where if the first $A(k)$ Fourier coefficients of a modular form of weight $k$ for $\textrm{SL}_2(\mathbb{Z})$ are nonnegative, then all of its Fourier coefficients are nonnegative, so that $A(k)$ can be interpreted as a ``nonnegativity Sturm bound''. We give upper and lower bounds for $A(k)$, as well as an upper bound on the $n$th Fourier coefficient of any form with no negative Fourier coefficients.
format Preprint
id arxiv_https___arxiv_org_abs_2507_17949
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Modular Forms with Only Nonnegative Coefficients
Jenkins, Paul
Rouse, Jeremy
Number Theory
11F11, 11F30
We study modular forms for $\textrm{SL}_2(\mathbb{Z})$ with no negative Fourier coefficients. Let $A(k)$ be the positive integer where if the first $A(k)$ Fourier coefficients of a modular form of weight $k$ for $\textrm{SL}_2(\mathbb{Z})$ are nonnegative, then all of its Fourier coefficients are nonnegative, so that $A(k)$ can be interpreted as a ``nonnegativity Sturm bound''. We give upper and lower bounds for $A(k)$, as well as an upper bound on the $n$th Fourier coefficient of any form with no negative Fourier coefficients.
title Modular Forms with Only Nonnegative Coefficients
topic Number Theory
11F11, 11F30
url https://arxiv.org/abs/2507.17949