Superdiffusion in optically controlled active media

Active media are complex systems driven by both thermal fluctuations and additional energy sources and are encountered in a variety of phenomena including mobile bacteria, protein diffusion or turbulent flows. However, studying the non-equilibrium dynamics of active media is often difficult because of their size and complexity. Here, we demonstrate that an active medium can be realized and controlled optically through dynamic coupling between multiply scattered light and colloidal particles. As a result of a strong light-matter interaction, the particles undergo diffusion upon a spatiotemporal random potential that leads to an apparent superdiffusion over timescales controlled by, among other things, both the input power and particle size. This model could serve as a convenient tool for exploring the intricacies of non-equilibrium thermodynamics of soft matter while also offering new possibilities for the coherent control of strongly coupled, complex systems. © 2012 Macmillan Publishers Limited. All rights reserved

Classical Results and Modern Approaches to Nonconservative Stability

Stability of nonconservative systems is nontrivial already on the linear level, especially, if the system depends on multiple parameters. We present an overview of results and methods of stability theory that are specific for nonconservative applications. Special attention is given to the topics of flutter and divergence, reversible- and Hamiltonian-Hopf bifurcation, Krein signature, modes and waves of positive and negative energy, dissipation-induced instabilities, destabilization paradox, influence of structure of forces on stability and stability optimization