Isomorphism between Jacobi forms of index $D_{2n+1}$ and elliptic modular forms of level $2$

Fuente: arXiv
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Autore principale: Hayashida, Shuichi
Natura: Preprint
Pubblicazione: 2025
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author Hayashida, Shuichi
author_facet Hayashida, Shuichi
contents This paper has three main objectives: (i) To establish an isomorphism between Jacobi forms of index $D_{2n+1}$ (lattice index) and elliptic modular forms of level $2$. (ii) To provide an explicit formula for the Fourier coefficients of Jacobi--Eisenstein series of index $D_{2n+1}$. (iii) To construct a holomorphic modular form of weight $3/2$ and level $8$ (and $4$) from the Zagier--Eisenstein series $\mathscr{F}$ of weight $3/2$ and level $4$. Moreover, we show that the four functions $E^*_2$, $η^3$, $θ^3$ and $\mathscr{F}$ have essentially the same Hecke eigenvalue $1+p$ for any odd prime $p$, where $E^*_2$ is the non-holomorphic Eisenstein series of weight $2$, $η$ is the Dedekind eta-function and $θ$ is the usual theta function. This fact arises as a special case of the isomorphism of (i).
format Preprint
id arxiv_https___arxiv_org_abs_2512_15012
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Isomorphism between Jacobi forms of index $D_{2n+1}$ and elliptic modular forms of level $2$
Hayashida, Shuichi
Number Theory
Primary 11F50, Secondary 11F37, 11F20, 11F46
This paper has three main objectives: (i) To establish an isomorphism between Jacobi forms of index $D_{2n+1}$ (lattice index) and elliptic modular forms of level $2$. (ii) To provide an explicit formula for the Fourier coefficients of Jacobi--Eisenstein series of index $D_{2n+1}$. (iii) To construct a holomorphic modular form of weight $3/2$ and level $8$ (and $4$) from the Zagier--Eisenstein series $\mathscr{F}$ of weight $3/2$ and level $4$. Moreover, we show that the four functions $E^*_2$, $η^3$, $θ^3$ and $\mathscr{F}$ have essentially the same Hecke eigenvalue $1+p$ for any odd prime $p$, where $E^*_2$ is the non-holomorphic Eisenstein series of weight $2$, $η$ is the Dedekind eta-function and $θ$ is the usual theta function. This fact arises as a special case of the isomorphism of (i).
title Isomorphism between Jacobi forms of index $D_{2n+1}$ and elliptic modular forms of level $2$
topic Number Theory
Primary 11F50, Secondary 11F37, 11F20, 11F46
url https://arxiv.org/abs/2512.15012