"Spectral Stability of Traveling Water Waves" David P. Nicholls Department of Mathematics, Statistics, and Computer Science University of Illinois at Chicago Chicago, IL 60607 Abstract -------- The motion of the free surface of an ideal fluid under the effects of gravity and capillarity arises in a number of problems of practical interest, consequently, the reliable and accurate numerical simulation of these "water waves" is of central importance. Recently, an efficient, stable, and high-order Boundary Perturbation scheme for simulating these traveling water waves (due to the author and F. Reitich) has been extended to address the equally important topic of their dynamic (spectral) stability. In this talk we will discuss this algorithm and present new results on the "motion" of the spectrum of the linearized water wave equations as the traveling waveform is varied. In particular, we will focus upon the radius of convergence of a Taylor series expansion of the spectral data and its possible connection to spectral instability of traveling water waves.