Complex plasmas — A kinetic view on thermo- and hydro-dynamics

Summary form only given. Complex plasma is the so called plasma state of soft matter. It is usually comprised of low temperature gas discharge and dust, often called dusty plasma. In our laboratory experiments we use capacitively coupled radio frequency (rf) discharges in noble gasses into which we inject mono disperse spherical particles which are a few micrometers in diameter. These particles charge up negatively and their surface potential is shielded by the surrounding plasma. The particles are trapped in the plasma by the plasma potential, under gravity they are levitated in the plasma sheath above the lower electrode. Complex plasmas are used as models to study atomistic systems, e.g. fluids, crystals, plasma, where they provide spatial magnification (the micro particles are visible by eye) and high temporal resolution (all relevant frequencies are below kHz). We will present current research using complex plasmas to experimentally investigate kinetic theories of thermodynamics as well as hydrodynamics. Complex plasmas are dissipative, open non-hamiltonian systems. They present themselves to the study of nonequilibrium thermodynamics and of dissipative structures (e.g. self organization or dissipative solitons). Due to tunable external forces and dissipation it is possible to observe the dynamics of and transitions between non-equilibrium phase transitions as well as the convergence of the system towards equilibrium. Currently we describe our world using continuous models, like hydrodynamics, even though the general understanding is that our world is made up of discrete atoms. So far there exists no theory to go all the way from the kinetics of single atoms to the laws of hydrodynamics, or the other way around. Complex plasmas seem to offer the opportunity to investigate fluids and fluid phenomena from the viewpoint of fully resolved single particle kinetics. There is a need for new kinetic theories for hydrodynamical properties, similar to the current develo- ment of kinetic viscosity in granular media.