Overview


 Soft matter includes colloidal suspensions, polymers, gels, liquid crystals, membrane systems, protein solutions, granular matter, and so on. Many of them have complex internal structures with mesoscopic length scales, leading to slow structural relaxations and sensitivity to external perturbations. As marked examples, we may even mention simple systems without internal structures such as near-critical fluids with enormous critical fluctuations and dense binary particle systems with size dispersity undergoing jamming or glass transition. The field of soft matter can cover a vast range of highly interdisciplinary problems and its border is being expanded in various directions by many people attacking their traditional and new problems.

 Now a wide variety of systems have been studied, where we often observe nonlinear and nonequilibrium phenomena on mesoscopic space-time scales. It is obvious that soft matter physics has been much influenced by the successful “coarse-graining” approaches in the research of critical phenomena. Of course, in soft matter physics, coarse-graining methods need to be based on full understanding of the microscopic molecular interactions. Conspicuous examples attracting attention are the cooperative effects resulting from ion-water and hydrogen-bonding interactions.

 In soft matter physics, we may tackle dynamical couplings involving multi-component variables, which are typically far more complex than those in the conventional phase transition dynamics. For example, in viscoelastic phase separation and shear-induced phase separation in entangled polymer solutions, relevant are dynamic couplings among concentration, velocity, and stress fields. Dynamic couplings among many degrees of freedom on different levels have also been recognized in electrophoretic motion of soft matter, dynamics of soft matter in liquid crystal solvent, solvation effects on phase transitions, active matter coupled with fluid motions, and so on. Thus, in soft matter, mesoscopic equilibrium and nonequilibrium structures (of various microscopic origins) emerge ubiquitously and have been studied extensively. In metallurgy, such mesoscopic objects have also been most crucial at structural phase transitions and plastic deformations. The same spirit and approaches should also be introduced in other fields of physics and chemistry, such as mesoscopic dynamics in strongly correlated electron systems, chemical reaction dynamics, and solvation dynamics, whose treatments have mostly been solely microscopic.

 In this workshop, we aim to survey these trends of soft matter physics. But we further wish to generate new ideas and streams towards deeper and wider understanding of the varied dynamics in soft matter.