“Chimeras” come to life in the lab

The sculpture shown here depicts a chimera, a fire-breathing monster of Greek mythology that’s part lion, part goat, and part serpent. In the parlance of nonlinear dynamics, a chimera state refers to a similarly incongruent beast—a partly synchronized, partly incoherent system of coupled oscillators. It’s been shown, in theory at least, that chimera states can exist, but they’ve proved difficult to spot in the real world. Now they’ve made their laboratory debut in two nearly simultaneous experiments—one led by Rajarshi Roy at the University of Maryland, College Park, and the other by Kenneth Showalter at West Virginia University. The Maryland researchers used a spatial light modulator to shape a laser beam’s wavefront. Based on the resulting image, they imposed a feedback that couples the phase delays imposed by neighboring pixels in the modulator. For certain coupling strategies, the beam adopted a partially coherent, partially incoherent state. By contrast, the West Virginia team exploited an oscillating chemical reaction in which catalyst-coated particles cyclically turn orange and green. Because the reaction is photosensitive, each cycle’s phase could be manipulated—and the particles coupled—by controlling each particle’s exposure to light. Appropriate coupling gave rise to a chimera state in which just half of the particles synchronized. The newly observed phenomenon may be much more than a curiosity; it closely resembles dynamical states seen in neural networks. (M. R. Tinsley, S. Nkomo, K. Showalter, Nat. Phys. 8, 662, 2012 ; A. M. Hagerstrom et al., Nat. Phys. 8 ,658, 2012 .)—Ashley G. Smart