Heidelberg 1999 – scientific programme

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PV: Plenarvorträge

PV VII

PV VII: Plenary Talk

Wednesday, March 17, 1999, 15:00–15:30, CH 1

One Hundred Years of Nonequilibrium Patterns — •Pierre Hohenberg — Department of Physics, Yale University New Haven, CT 06520-8120, USA

Among the simplest macroscopic nonequilibrium systems are spatially uniform ones in which energy is fed in at a steady or periodic rate. Examples are a horizontal layer of fluid heated from below (Rayleigh-Benard convection), a cylinder filled with fluid and rotated about its axis (Taylor-Couette flow), or a layer of fluid placed on a vibrating plate (Faraday waves), as well as a large number of other chemical, biological and physical systems. In the above examples the control parameter R, describing the rate at which energy is fed into the system is, respectively, the temperature difference between the top and bottom plates of the layer, the rotation frequency of the cylinder, and the amplitude of oscillation of the vibrating plate. In a typical scenario the system remains uniform for small R, but the homogeneous state undergoes a linear instability at a critical value Rc, above which a spatial pattern emerges and grows. Initially this pattern is often spatially regular and either stationary or periodic in time. As R increases new instabilities and patterns occur, with increasing manifestations of disorder in space and time. Examples of regular and irregular phenomena that will be discussed include pattern selection, pulse and front propagation, and spatiotemporal chaos.