Worms in Electroconvection of Nematic Liquid Crystals

Experimentally localized traveling-wave structures in the form of "worms" have been observed by M. Dennin, G. Ahlers and D.S. Cannell (PRL 77 (1996) 2475). Below are two top views, one showing a single long worm and the other showing a number of snapshots of larger parts of the system.


Since the bifurcation to the extended traveling waves is supercritical the usual Ginzburg-Landau equations are not sufficient to describe these localized waves below threshold. An extension similar to that used for binary-mixture convection explains the localization mechanism and gives qualitatively similar solutions (H. Riecke and G.D. Granzow, Phys. Rev. Lett. 81 (1998) 333).


In larger systems a number of these worms can appear and exhibit a typical distance in the y-direction.


Through the interaction with an additional mode the supercritical traveling waves become localozed in worms.


Movies of worm evolution:
Steady worm (700Kb). The height indicates the strength of the additional field that is responsible for the localization of the wave. The color map gives the wave as it would be seen in the experiment.
Start from small random initial conditions (400kB) without dispersion. Color and height indicate the strength of the additional field C. Laterally the additional field C suppresses convection (blue color indicates negative values of C). The wave character is as in the movie of the steady worm.
2d ("top view") of the same run starting from random initial condition.
Unsteady worm (520Kb) due to dispersion. Smaller version (300Kb).

Research supported by DOE and NSF.

May 30, 1999