I have conducted the following research with collaborators:
Two problems concerning connectivity and extremal graph theory;
Three problems on the characterization of digraphs under common neighbor conditions;
Two related problems in combinatorial matrix theory, discrete algorithms, where the latter builds upon the results of the former;
One problem related to graph planarity;
Two problem concerning competition graphs and their variants.
Submitted Papers & Preprints
Connectivity keeping trees in triangle-free graphs
(with Shinya Fujita, Boram Park, Homoon Ryu), arxiv:2511.06622
On 2-connected graphs avoiding cycles of length 0 modulo 4
(with Boram Park, Homoon Ryu), arxiv:2507.12798
Linear-time computation of the Frobenius normal form for symmetric Toeplitz matrices via graph-theoretic decomposition
(with Homoon Ryu), arxiv:2505.20811
Competition-common enemy graphs of degree-bounded digraphs
(with Myungho Choi, Suh-Ryung Kim), arxiv:2405.13363
Digraphs in which every t vertices share exactly λ out-neighbors and exactly λ in-neighbors
(with Suh-Ryung Kim), arxiv:2405.13293
Planarity of generalized ladder graphs
(with Suh-Ryung Kim, Homoon Ryu), arxiv:2208.13637
Accepted & Published Papers
Digraphs in which every t vertices have exactly λ common out-neighbors (with Myungho Choi, Suh-Ryung Kim),
Discrete Mathematics, 348(10):114580 (2025), arxiv
Structural properties of symmetric Toeplitz and Hankel matrices (with Homoon Ryu),
Linear Algebra and its Applications, 708:204-216 (2025), arxiv
A digraph version of the Friendship Theorem (with Myungho Choi, Suh-Ryung Kim),
Discrete Mathematics, 348(1):114238 (2025), arxiv
Competition graphs of degree bounded digraphs (with Suh-Ryung Kim),
Discrete Applied Mathematics, 343:106-114 (2024), arxiv
For this research, I received a grant (with the same title) from Basic Science Research Program, National Research Foundation of Korea (KRW 20,000,000).
🧑🧑🧒🧒 List of co-authors (# papers with me)
Myungho Choi (3), Shinya Fujita (1), Suh-Ryung Kim (6), Boram Park (2), Homoon Ryu (5)
🌿 Where Problems Grow (and Sometimes Bloom)
Open Problem Garden (Graph Theory)
Erdös' Problems on Graphs from UCSD
Erdös' Problems made by Thomas Bloom
