The
Elusive Chimera By Rebecca Herod Photo by Brian Persinger
The chimera of mythology is a fire-breathing beast composed of the heads of a lion, goat, and snake. In the world of nonlinear dynamics, the reproduction of the chimera state, a partly synchronized, partly asynchronous system of coupled oscillators, has been as elusive to spot as the fictional Greek monster. Recently the chimera state has been reproduced in two simultaneous experiments—one led by Rajarshi Roy, professor of physics and director of the Institute for Physical Science and Technology at the University of Maryland, College Park and the other by Professor and C. Eugene Bennett Chair in Chemistry Kenneth Showalter, in the C. Eugene Bennett Department of Chemistry. Roy and Showalter, longtime friends working separately in two different disciplines, are the first ever to recreate the elusive 1
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theoretical chimera state in the laboratory. “Since 2002, mathematicians and physicists have been actively investigating the chimera state because it is very unusual for a system that is partly synchronized and partly unsynchronized to be stable,” Showalter said. “We are excited to demonstrate this behavior in an experimental system, which also showed new features. It’s also great fun to have our report appear simultaneously with the report from my friend and colleague Raj Roy.” Showalter and his WVU research collaborators, Research Assistant Professor Mark Tinsley, PhD, and Simbarashe “Simba” Nkomo, a doctoral student from Zimbabwe, have published their 3
findings in the prestigious journal Nature Physics. The three researchers designed the experiment together, while Tinsley was the lead on the computer simulations and Nkomo carried out the experiments. A chimera state is a balanced system made up of synchronous and asynchronous oscillators. Oscillators are anything that exhibits cyclical behavior—AC circuits, neurons, cells, even clocks. When two or more oscillators interact, they can synchronize. For example, pendulum clocks placed on the same wall tend to keep time at the exact same pace. Cardiac pacemaker cells in the human heart fire at the same rate, resulting in spontaneous synchronization and a regular heartbeat. 4
Population of coupled chemical oscillators exhibiting two subpopulations (red and gray), which are synchronized in-phase (1), synchronized out-of-phase (2), synchronized with one and two phase-cluster states (3), and with synchronized and unsynchronized states–the chimera state (4) for different intra- and inter-group coupling strengths. 56
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Eberly College of Arts and Sciences Magazine