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arXiv · 2606.22458

Eichler-Selberg relations for the third-order mock theta functions

Wei Wang
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Abstract

Ramanujan's third-order mock theta function $f(q)$ admits the well-known Appell-Lerch series representation: \[ \sum_{n=0}^{\infty}\frac{q^{n^2}}{(-q;q)_n^2}=\frac{2}{(q;q)_{\infty}}\sum_{n=-\infty}^{\infty}\frac{(-1)^nq^{\frac{3}{2}n^2+\frac{1}{2}n}}{1+q^n}. \] In this paper, we establish a natural generalization of this classical identity by utilizing the theory of harmonic Maass forms. Furthermore, we prove analogous Eichler-Selberg type relations for another third-order mock theta function $\omega(q)$. The method presented in this paper can be extended to study other classes of mock theta functions.

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Wei Wang. 2026-06-21. Eichler-Selberg relations for the third-order mock theta functions. https://arxiv.org/abs/2606.22458

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