Professor at Department of Mathematics, Capital Normal University (首都师范大学数学系).
105 Xisanhuan Beilu, Haidian District, Beijing 100048, P. R. China.（北京市海淀区西三环北路105号，100048）
E-mail: sunsz AT cnu.edu.cn
I graduated from Chern Institute of Mathematics, Nankai University, Tianjin and got my PhD degree in 2001.
I spent two years from 2001 to 2003 at School of Mathematical Sciences, Peking University as postdoc.
Then I joined Capital Normal University in 2003 as a faculty member of Department of Mathematics.
Here is my CV (to be added).
My research interests lie at the crossroads of mathematics and physics, and I work on such topics as N-body problem in celestial mechanics, Fukaya category in symplectic topology, semiclassical trace formula and resurgence theory.
More precisely, I am interested in
Symplectic Geometry and Symplectic Topology: symmetry and symplectic reduction; Floer homologies and Fukaya categories; quiver varieties; cluster varieties; singularities from symplectic perspective; symplectic nature of moduli spaces (e.g. Hitchin moduli space); noncommutative symplectic/Poisson geometry; derived symplectic/Poisson geometry;
Hamiltonian Systems and Celestial Mechanics: Lagrangian Grassmannian and Maslov index; N-body problem (stability; central configurations; periodic orbits); Gutzwiller’s semiclassical trace formula and quantum chaos; (algebraic) completely integrable Hamiltonian systems (ACIS) and their interactions with geometry and physics
Mathematical Physics: higher structures (homological/homotopical algebras, higher categories,…) behind quantum mechanics and quantum field theory; quantization (semiclassical, deformation quantization, BV, brane quantization…); Feynman diagrams; modular objects; gauge theory;
Resurgence Theory and Mould Calculus à la Écalle with applications in mathematics (BCH, MZV, modularity…) and quantum physics (wall-crossing, Écalle-Voros exact WKB analysis, complex Chern-Simons theory, topological string theory…)
Autumn 2026
Calculus III (Multivariables)
Granduate course: Symplectic Geometry and Symplectic Topology
Reading seminar: Gutzwiller’s classic “Chaos in classical and quantum mechanics”
Working seminar: wild character variety, spectral network, Fukaya category, microlocal sheaf, HyperKahler, resurgence and mould
天体力学数学理论研讨会（系列，2019年始）
科普报告（2017年始）
讨论班报告
题目：Hamiltonian Monodromy and Singular Lagrangian Fibrations in Three Degrees of Freedom
摘要：Hamiltonian monodromy is one of the most fundamental topological invariants of integrable Hamiltonian systems, measuring the obstruction to the existence of global action-angle coordinates. Although its theory is well developed for systems with two degrees of freedom, less is known about the topology of singular Lagrangian fibrations in higher dimensions. In this talk I will discuss two examples that reveal new phenomena in three-degree-of-freedom integrable systems. The first example is an integrable Hamiltonian system near an elliptic equilibrium in 1:1:-2 resonance. The integrability of the system originates from averaging along the periodic motion of the quadratic part and an imposed rotational symmetry about the vertical axis. Introducing a detuning parameter we find a rich bifurcation diagram, containing three families of Hamiltonian Hopf bifurcations that join at the origin. I describe the monodromy of the resulting ramified 3-torus bundle as variation of the detuning parameter lets the system pass through the 1:1:-2 resonance. The second example is a classical two-spin Tavis–Cummings system. The system has a singular fiber homeomorphic to S^2 x S^1 with an A_2-type singularity. This provides the first physical realization of an integrable Hamiltonian system with a singularity that goes beyond the familiar focus-focus. We describe in detail the topology of the corresponding singular Lagrangian fibration, compute its monodromy, and we discuss the connections with standard singularity theory. References：（1）K. Efstathiou, H. Hanßmann, and A. Marchesiello. “Bifurcations and Monodromy of the Axially Symmetric 1:1:-2 Resonance”. In: Journal of Geometry and Physics 146, p. 103493 (2019). （2）K. Efstathiou, G. J. Gutierrez-Guillen, P. Mardesic, and D. Sugny. “Hamiltonian Monodromy in a Tavis-Cummings System with an A_2 Singularity”. arXiv:2604.14835(2026).
报告人：Konstantinos Efstathiou（昆山杜克大学）
时地：2026年8月3日（周一）上午10:30-11:30，首都师范大学本部新教二楼612教室