A modular framework of generalized Hurwitz class numbers
| Autor: | Beckwith, Olivia, Mono, Andreas |
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| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | We discover a non-trivial rather simple relation between the mock modular generating functions of the level $1$ and level $N$ Hurwitz class numbers. This relation yields a holomorphic modular form of weight $\frac{3}{2}$ and level $4N$, where $N > 1$ is stipulated to be odd and square-free. We extend this observation to a non-holomorphic framework and obtain a higher level non-holomorphic Zagier Eisenstein series as well as a higher level preimage of it under the Bruinier--Funke operator $\xi_{\frac{1}{2}}$. All of these observations are deduced from a more general inspection of a certain weight $\frac{1}{2}$ Maass--Eisenstein series of level $4N$ at its spectral point $s=\frac{3}{4}$. This idea goes back to Duke, Imamo\={g}lu and T\'{o}th in level $4$ and relies on the theory of so-called sesquiharmonic Maass forms. We calculate the Fourier expansion of our sesquiharmonic preimage and of its shadow. We conclude by offering an example if $N=5$ or $N=7$ and we provide the SAGE code to compute the Fourier coefficients involved. Comment: 32 pages in total, including an appendix with program code (see ancillary file as well), no figures. Comments welcome! |
| Databáze: | arXiv |
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