English

Modules of Jacobi forms of degree two of small levels

Number Theory 2026-02-23 v1

Abstract

The purpose of this paper is to describe explicitly the modules of (Siegel-)Jacobi forms of degree two of index one of any scalar valued weight with respect to some congruence subgroups of small levels N4N\leq 4. Such a structure for the full Siegel modular group as a module over scalar valued Siegel modular forms of even weight has been explicitly given by T.~Ibukiyama. There we used an explicit structure theorem of rings of scalar valued Siegel modular forms by Igusa and that of vector valued Siegel modular forms of weight detk\Sym2\det^k\, \Sym^2 by T. Satoh and T. Ibukiyama. On the other hand, for levels N=2N=2, 33, 44, ring structures of scalar valued case have been also known by H. Aoki and T. Ibukiyama and detk\Sym2\det^k \Sym^2-valued case by H. Aoki. In this paper, by merging these results, we give the same sort of simple structure theorems on modules of Jacobi forms of degree of two of index one for level 22, 33 and 44.

Keywords

Cite

@article{arxiv.2602.18017,
  title  = {Modules of Jacobi forms of degree two of small levels},
  author = {Hiroki Aoki and Tomoyoshi Ibukiyama},
  journal= {arXiv preprint arXiv:2602.18017},
  year   = {2026}
}