Theoretical Physics Seminar:
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Sep 07, 2007 11:00 AM, Theoretical Physics
Dissipative quantum systems: exact results.
Speaker: Vladimir Bazhanov
Abstract: Over the last fifteen years several exact results were obtained for the so-called boundary sine-Gordon model. In the conformally symmetric case this two-dimensional quantum field theory describes a one-dimensional quantum Brownian motion in a periodic (cosine) potential. The massless bulk 2D field plays the role of the Caldeira-Leggett quantum heat bath with ohmic dissipation. The model finds many application to problems of quantum tunneling in presence of a strong coupling to the dissipative environment. For example, it describes the tunneling of the fractionally charged edge excitations through a point contact in the quantum Hall effect. It also describes a dissipation-driven superconductor-insulator phase transition in resistively shunted Josephson junctions. In my talk I will give a review of the theory of quantum Brownian motion. I will discuss the Langevin and Fokker-Plank equations in the classical case, the Feynman-Vernon-Caldeira-Leggett theory of the quantum thermostat, then move on to the Schwinger-Keldysh approach to a non-equilibrium transport in quantum systems. Finally I will derive the exact expression for the non-linear mobility for a dissipative quantum particle moving in a ``washboard'' potential at arbitrary bias and temperature. The talk is indented for a general physical and mathematical audience, no specialized knowledge will be required. This talk is based on the results previously obtained by V.Bazhanov, S.Lukyanov and A.Zamolodchikov.
