T. Ibukiyama

activity

20242026

collaborators

5 papers

math.NT2026

Harder's conjecture II

Hiraku Atobe, Masataka Chida, Tomoyoshi Ibukiyama +2

Let $f$ be a primitive form of weight $2 k + j - 2$ for $S L_{2} (Z)$ , and let $P$ be a prime ideal of the Hecke field of $f$ . We denote by $S p_{m} (Z)$ the Siegel modular group of degree $m$ .…

math.NT2026

Modules of Jacobi forms of degree two of small levels

Hiroki Aoki, Tomoyoshi Ibukiyama

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 subg…

math.NT2025

Hermitian modular forms and algebraic modular forms on $S O (6)$

Tomoyoshi Ibukiyama, Brandon Williams

We state conjectures that relate Hermitian modular forms of degree two and algebraic modular forms for the compact group $S O (6)$ . We provide evidence for these conjectures in the f…

math.NT2025

When is a polarised abelian variety determined by its $p$ -divisible group?

Tomoyoshi Ibukiyama, Valentijn Karemaker, Chia-Fu Yu

We study the Siegel modular variety $A_{g} \otimes F_{p}$ of genus $g$ and its supersingular locus $S_{g}$ . As our main result we determine precis…

math.NT2024

Formal series of Jacobi forms

Hiroki Aoki, Tomoyoshi Ibukiyama, Cris Poor

We prove for general paramodular level that formal series of scalar Jacobi forms with an involution condition necessarily converge and are therefore the Fourier-Jacobi expansions a…