J. Koo

collaborators

4 papers

math.NT2026

Adelic framed form class groups and explicit class field theory

Ja Kyung Koo, Dong Hwa Shin, Dong Sung Yoon

Let $D$ be a negative discriminant, and let $K = Q (D)$ . Let $Q (D)$ denote the set of primitive positive definite binary quadratic forms over $Z$ of…

math.NT2026

On the integrality of modular functions over $Z [j]$ and Kronecker-type congruences

Ho Yun Jung, Ja Kyung Koo, Dong Hwa Shin

Let $N$ be a positive integer and let $f$ be a meromorphic modular function of level $N$ with rational Fourier coefficients. For a prime $p$ , define a function $f_{p}$ on the complex…

math.NT2025

A simplified algorithmic realization of Galois actions on special values of modular functions

Ja Kyung Koo, Dong Hwa Shin, Dong Sung Yoon

We propose an explicit and practical algorithm for computing Galois conjugates and irreducible polynomials for special values of modular functions evaluated at CM points associated…

math.NT2025

Inverse limits of CM points on certain Shimura varieties

Ho Yun Jung, Ja Kyung Koo, Dong Hwa Shin

Let $N$ be a positive integer, and let $D \equiv 0$ or $1\Mod{4}$ be a negative integer. We define the sets $CM (D, Y_{1} (N)^{\pm})$ and $CM (D, Y (N)^{\pm})$ as subsets…

Adelic framed form class groups and explicit class field theory

On the integrality of modular functions over Z[j] and Kronecker-type congruences

A simplified algorithmic realization of Galois actions on special values of modular functions

Inverse limits of CM points on certain Shimura varieties

On the integrality of modular functions over $Z [j]$ and Kronecker-type congruences