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NEWS | Nov. 30, 2017

Dr. Thomas Carroll Elected Fellow of the American Physical Society

By Daniel Parry

WASHINGTON – Dr. Thomas Carroll, research physicist in the Center for Computational Materials Science at the U.S. Naval Research Laboratory (NRL), has been elected a Fellow of the American Physical Society (APS). Carroll is recognized by the APS for research in nonlinear dynamics including experimental detection of transient chaos in magnetic spin-wave materials, synchronization of chaotic systems, applications of chaos to communications and radar, and applying phase space techniques to signal analysis.

“I would like to thank my mentor and supervisor, Dr. Lou Pecora, for this outstanding nomination," said Carroll. “I would also like to thank everyone at NRL who created the environment that allowed me to do all the good basic research that led to this award.”

Carroll received a Bachelor of Arts in physics from Carleton College, Northfield, Minnesota, in 1981 and a doctorate in physics from the University of Illinois at Urbana-Champaign in 1987. His thesis used optical spectroscopy to investigate the effects of high pressure on metal-metal bonds in molecular crystals.

Coming to NRL in 1987 as an American Society for Engineering Education (ASEE) postdoc, under the supervision of Pecora, Carroll’s first project was studying ferromagnetic resonance in yttrium iron garnet spheres. He made one of the first experimental observations of chaotic transients, and by measuring the transient lifetimes as a function of magnetic field, was able to produce the first confirmation of a theory relating transient lifetime to a bifurcation parameter. This confirmed the existence of a phenomenon that had been suspected, but not yet observed, and showed that transient behavior in a physical system is possible on time scales (hours) different from typical magnetic dynamics (micro-seconds). This became the first of many Physical Review Letters for Carroll.

In 1990, Carroll and Pecora developed a method to synchronize chaotic systems, which they confirmed with simulations and experiments. This greatly stimulated research into the uses of chaos for communication and resulted in a Physical Review Letter that is now the 11th most cited paper in Physical Review Letters.

“The research described in this paper was a breakthrough on how to construct a new dynamical system in which two chaotic systems came into complete synchrony,” said Pecora. “This caused an avalanche of research, leading to another ground-breaking paper by Carroll on synchronizing dynamical systems in arbitrarily structured networks.”

Carroll devised other forms of chaotic synchronization for coupled oscillators and was the first to experimentally demonstrate riddled basins, a nonlinear phenomenon predicted some years before, but not observed.

His coupled oscillator work led to the master stability function method for coupled oscillators, solving the stability problem for synchronizing chaotic oscillators in one step that then applies to any network structure of those oscillators. “This method has populated over 6000 citations in the Physical Review Letters and is widely used today in dynamical systems research,” Pecora added.

Carroll's work on overcoming the effects of noise on chaotic synchronization demonstrated a noise-robust chaotic system that also suggests how a neuron transmits information efficiently in the presence of noise. Carroll’s work on this topic continues today with an alternative approach to synchronizing chaotic systems that works in noisy environments. His work has also employed phase space methods for analyzing signals from radios, radars, or other sources. Recently, Carroll applied Bayesian statistical techniques to chaotic attractors making efficient comparisons of attractors possible even in cases where noise exists in the signals, which led to a way to estimate the embedding dimension for an attractor using no adjustable parameters.

Carroll has studied the use of chaos for communication, synchronization of coupled nonlinear oscillators, and applications of nonlinear dynamics methods to signal processing problems in radar and electronic warfare and has over 150 publications and 10 patents. He continues his work at NRL in the areas of signal processing, analysis, and synthesis.

The APS Fellowship Program recognizes members who have made advances in knowledge through original research and publication or made significant and innovative contributions in the application of physics to science and technology.

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