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This talk concerns the rigorous derivation of diffusion, thermalization and decoherence in simple quantum systems: a spin or a particle interacting with phonons. Our approach takes the Markovian description (Pauli master equation or quantum Boltzmann equation) as a starting point. However, since such a Markovian description is only valid in a certain scaling limit (vanishing coupling constant and long time), we develop an expansion around the Markovian description to control the behavior at finite coupling constant. This expansion consists of a controlled renormalization group flow with Brownian motion as the fix-point solution. The long-range nature of the velocity-velocity correlation function is an example of a physical quantity that is not described correctly within the Markovian description (cfr. Alder-Wainwright), but that is captured by our approach.

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Dr. Wojciech De Roeck, University of Cologne
Seminarraum Theoretische Physik
Contact: not specified