The pressure of active particles

For equilibrium systems pressure has been demonstrated to have a microscopic origin related to momentum of the particles. Through kinetic theory and statistical mechanics a link among macroscopic and microscopic world has been derived. When we leave the particular case of equilibrium a general theory does not exist yet and different nonequilibrium issue can lead to different results. In this talk I will focus on active particles, i.e. particles capable of converting (internal or environmental) energy into directed motion. Through this supply of energy due to internal degrees of freedom entails a non-conservation of mechanical energy and non-elasticity of interaction among particles, assumed condition on kinetic theory for derivation of the pressure on a wall. Therefore, we expect that pressure exerted by active particles could present new and stimulating features, due to the nonequilibrium nature of the microscopic model.