The study of collective behavior of many individual objects is not only relevant to the physical sciences but also to socio-economics. The relations among the many underlying units of such systems give rise to a challenging degree of complexity, which is typically reflected in nontrivial correlations and spontaneous emergence of collective properties.
Soft materials display a broad range of collective phenomena. The groups of Vitelli and Van Hecke (Leiden) study these phenomena with an emphasis on the physics of frustrated and amorphous materials such as granular media, foams, glasses and fibrous networks. Combining theory, experiments and simulations, Casimir researchers study how soft materials organize, and how this organization impacts their mechanical properties, such as vibrational modes, elasticity, shock waves, flow and failure.
Socio-economics: Garlaschelli's group (Leiden) develops an information-theoretic approach to the structure and dynamics of large networks, with an emphasis on socio-economic systems. The group has already shown that it is possible to use the properties of canonical ensembles in statistical mechanics in order to distinguish nontrivial topological patterns from randomness in real complex networks, and also to stochastically reconstruct the structure of networks from partial information. Future goals include extensions of the theory to financial time series and more complicated scenarios.