Research: Dynamical Systems
Dynamical systems are mathematical objects used to model physical phenomena whose state (or instantaneous description) changes over time.
Wolf, A., Swift, J. B., Swinney, H. L., & Vastano, J. A. (1985). Determining Lyapunov exponents from a time series. Physica D: Nonlinear Phenomena, 16(3), 285-317. (6000+ citations and counting!)