The focus of my research is the investigation of small systems. The properties of objects at the nanoscale are dominated by quantum effects and by thermal fluctuations. They are moreover strongly influenced by the coupling to external environments. The precise understanding of the dynamical effects induced by such a coupling is of central importance in most branches of physics, most prominently quantum optics, solid state physics and nonequilibrium statistical physics. The interaction with the environment can either perturb the evolution of the nanosystem -- and should therefore be minimized as much as possible -- or on the contrary can be used as a powerful tool to control its dynamics.

Here is a list of major environment-induced effects (classical and/or quantum-mechanical):

• diffusion and fluctuation phenomena

• relaxation and dissipation processes

• noise-induced transport (Brownian motors)

• decoherence and entanglement

The study of these various phenomena becomes particularly rich and challenging when system and/or environment are nonlinear or in some sense complex. I use a variety of theoretical tools to treat these different problems, including classical and quantum stochastics, fractional analysis, Lévy statistics and random-matrix theory to name a few.

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