The Challenge: Most practically successful machine learning models involve highly non-convex optimization problems, yet their landscapes remain poorly understood. Traditional optimization theory often fails to explain why gradient methods work so well in practice.
My Approach: I develop the theory of "hidden convexity" — the idea that many seemingly non-convex problems actually admit equivalent convex structures, even if these structures are not directly computable. This framework provides rigorous explanations for the surprising success of optimization methods and enables the design of global solution algorithms.
Key Contributions:
Impact: This line of work has led to substantial understanding of efficiency of policy gradient methods and provides a principled path for understanding non-convex optimization landscapes in safety-critical applications.
Learning Zero-Sum Linear Quadratic Games with Improved Sample Complexity and Last-Iterate Convergence. with J. Wu, A. Barakat, N. He. SIAM Journal on Control and Optimization, 2025.
Reinforcement Learning with General Utilities: Simpler Variance Reduction and Large State-Action Space. with A. Barakat, N. He. ICML, 2023.
Optimizing Static Linear Feedback: Gradient Method. with B. Polyak. SIAM Journal on Control and Optimization, 2021.
This theoretical framework has enabled breakthrough results in understanding why modern optimization methods work so well in practice, providing the mathematical foundations for reliable AI systems in safety-critical applications.