dc.description.abstract | Microscopically, the motion of liquid is stick-slip type at the discrete kinetic level, and the structure of cold liquid is not completely disordered. The competition between thermal perturbation and the strong mutual coupling interaction leads to the coexistence between ordered crystalline domain and disordered defect clusters. The boundary and orientation of these domains fluctuate due to the structural rearrangement induced by the intermittent stick-slip type motions of particles, which are composed of rattling in the cage formed by organized neighbors and the avalanche-like cooperative hopping with the indefinite magnitude.
From a more general view, the power-law distributed avalanches, including nature phenomena such as earthquakes, superconducting vortices, biological evolution, stock markets, are also strongly coupled nonlinear extended system. By the concept of “self-organized criticality (SOC)”, they are very unpredictable because the most minor persistent or stochastic perturbation can trigger the activation which cascades through the strong coupling to the whole system and gives rise to the cooperative motion. Though these systems cannot be long-term, exactly predicted, the spatiotemporal structure of coarse-graining can provide short-term information about how the system will evolve, which means that in an appropriate spatial-temporal scale, the correlation between structure and motion do exist.
We investigate experimentally the predictability of the avalanche type cooperative hopping in dusty plasma liquid. In this system, the negatively charged micrometer sized dusts are suspended in weakly ionized plasma, self-organized into quasi-2D liquids through strongly coupled Coulomb forces and thermal kicks. The dynamic microstructure and micromotion can be traced by direct optical microscopy.
It is found that there are correlation between the avalanche type cooperative hopping and the spatiotemporal structural changes. The short-term prediction can be achieved by coarse-grained bond orientational order, and by the intensity of high frequency caged rattling motion. The coupling between the structural change at larger length scale and the motional fluctuation at small time scale supports the scenario that the accumulation of constructive stochastic perturbation distorts the crystalline ordered domain, and therefore deteriorates the structural order, raises the structural heterogeneity. This is accompanied by the structural weakening and the lowering of cage potential formed by the strong coupling with neighbors, and the high frequency rattling motion becomes more violent.
| en_US |