Elasticity typically refers to a material's ability to store energy, whereas viscosity refers to a
material's tendency to dissipate it. In this review, we discuss fluids and solids for which this is …

When driven by nonequilibrium fluctuations, particle systems may display phase transitions
and physical behavior with no equilibrium counterpart. We study a two-dimensional particle …

We investigate how reliable movement can emerge in aggregates of highly error-prone
individuals. The individuals—robotic modules—move stochastically using vibration motors …

Whereas naturally occurring swarms thrive when crowded, physical interactions in robotic
swarms are either avoided or carefully controlled, thus limiting their operational density …

Elastic active matter—also called an active solid—consists of self-propelled units embedded
in an elastic matrix and it resists deformation. This shape-preserving property and the …

We investigate the physics of an open two-component Dicke model, where the light field
mediates nonreciprocal interactions between two spin species. We show that the model …

In an equilibrium thermal environment, random elastic collisions between background
particles and a tracer establish the picture of Brownian motion fulfilling the celebrated …

Thermal fluctuations constantly excite all relaxation modes in an equilibrium crystal. As the
temperature rises, these fluctuations promote the formation of defects and eventually …

Inertial effects affecting both the translational and rotational dynamics are inherent to a
broad range of active systems at the macroscopic scale. Thus, there is a pivotal need for …

We study the collective vibrational excitations of crystals under out-of-equilibrium steady
conditions that give rise to entropy production. Their excitation spectrum comprises …