Junghyun Lee ☕️

Junghyun Lee

PhD Candidate in Artificial Intelligence

Kim Jaechul Graduate School of AI, KAIST

About

I am a final-year PhD candidate at the Kim Jaechul Graduate School of AI, KAIST, where I am very fortunate to be advised by Se-Young Yun (OSI Lab) and Chulhee “Charlie” Yun (OptiML Lab). I spent the summer of 2025 as a Research Scientist Intern at Adobe Research, San Jose, working with Branislav “Brano” Kveton, Anup Rao, Subhojyoti Mukherjee, Ryan A. Rossi, Sunav Choudhary, and Alexa Siu. Before my PhD, I earned my MSc from the same school, and a BSc in Mathematical Sciences and Computer Science (double major, cum laude), also from KAIST.

My research focuses primarily on interactive machine learning (online learning, bandits, RL, active learning), “theoretical aspects” of LLMs (e.g., alignment, reasoning), optimization theory, deep learning theory, and statistical analyses of large networks with an emphasis on community detection. More broadly, I am interested in all aspects of mathematical and theoretical AI, as well as related problems in mathematics and statistics.

I enjoy organizing seminars and workshops to foster Korea’s theoretical AI community (see Organizer). Outside of research, I am an avid violinist and perform as a first violinist with various amateur orchestras, including the KAIST Orchestra (KAO), PASSIONATE Orchestra, MDOP Orchestra, KAO-S, PROJECT Starlight, and PROJECT IDEA.

Feel free to reach out if you’d like to collaborate on any of my research topics, or just to connect! (Third-person bio here.)

Education

PhD in Artificial Intelligence

2023 – Present

KAIST

MSc in Artificial Intelligence

2021 – 2023

KAIST

BSc in Mathematical Sciences & Computer Science

2017 – 2021 · cum laude

KAIST

Research Interests

Bandits, Online Learning Statistical Reinforcement Learning Theoretical Aspects of LLMs Statistics, Learning Theory Community Detection, Networks Deep Learning / Optimization Theory Algorithmic Fairness Distributed Algorithms
Featured Publications

Instance-Optimal Estimation with Multiple LLM Judges on a Budget

Evaluating large language models increasingly relies on LLM-as-a-judge protocols, but such evaluations remain costly: different judges have different prices and reliabilities, and …

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Junghyun Lee

Looking Through the Mirror: Minimax-Optimal Regularized Regrets in Online Learning and Bandits

We revisit regularized regret minimization under full-information and bandit feedback, where a learner optimizes an objective of the form $\langle r, \pi \rangle - \eta^{-1} …

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Junghyun Lee
GL-LowPopArt: A Nearly Instance-Wise Minimax-Optimal Estimator for Generalized Low-Rank Trace Regression featured image

GL-LowPopArt: A Nearly Instance-Wise Minimax-Optimal Estimator for Generalized Low-Rank Trace Regression

We present GL-LowPopArt, a novel Catoni-style estimator for generalized low-rank trace regression. Building on LowPopArt (Jang et al., 2024), it employs a two-stage approach -- …

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Junghyun Lee
Near-Optimal Clustering in Mixture of Markov Chains featured image

Near-Optimal Clustering in Mixture of Markov Chains

We study the problem of clustering T trajectories of length H, each generated by one of K unknown ergodic Markov chains over a finite state space of size S. The goal is to …

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Junghyun Lee

Provably Efficient Regularized Online RLHF with Generalized Bilinear Preferences

We consider the problem of *regularized* best-response max-regret minimization in online RLHF under general preferences and bandit feedback. While various regularizers are utilized …

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Junghyun Lee
Recent Publications

Browse and filter all publications on the Publications page.

Contact

Find Me

KAIST Seoul Campus, Building 9 (9508 & 9410)

85 Hoegi-ro, Dongdaemun-gu

Seoul 02455, Republic of Korea