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arXiv · 2301.11901

Sums of Cusp Form Coefficients Along Quadratic Sequences

Chan Ieong Kuan·David Lowry-Duda·Alexander Walker·Raphael S. Steiner
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Abstract

Let $f(z) = \sum A(n) n^{(k-1)/2} e(nz)$ be a cusp form of weight $k \geq 3$ on $\Gamma_0(N)$ with character $\chi$. By studying a certain shifted convolution sum, we prove that $\sum_{n \leq X} A(n^2+h) = c_{f,h} X + O_{f,h,\epsilon}(X^{\frac{3}{4}+\epsilon})$ for $\epsilon>0$, which improves a result of Blomer from 2008 with error $X^{\frac{6}{7}+\epsilon}$. This includes an appendix due to Raphael S. Steiner, proving stronger bounds for certain spectral averages.

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Chan Ieong Kuan, David Lowry-Duda, Alexander Walker, Raphael S. Steiner. 2023-01-27. Sums of Cusp Form Coefficients Along Quadratic Sequences. https://arxiv.org/abs/2301.11901

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