Symbolic approach for measuring temporal "irreversibility"

We describe a symbolic approach for measuring temporal "irreversibility" in time-series measurements. Temporal irreversibility is important because it excludes Gaussian linear dynamics and static transformations of such dynam ics from the set of possible generating processes. A symbolic method for me asuring temporal irreversibility is attractive because it is computationall y efficient, robust to noise, and simplifies statistical analysis of confid ence limits. We propose a specific algorithm, called "false flipped symbols ," for establishing the presence of temporal irreversibility without the ne ed for generating surrogate data. Besides characterizing experimental data, our results are relevant to the question of selecting alternative models. We illustrate our points with numerical model output and experimental measu rements.