Regensburg 2007 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 12: Statistical physics (general)
DY 12.5: Vortrag
Dienstag, 27. März 2007, 11:00–11:15, H3
Fluctuations in subsystems of the zero temperature XX chain: emergence of an effective temperature — •Viktor Eisler1, Örs Legeza2, and Zoltan Racz3 — 1Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany — 2Research Institute for Solid State Physics and Optics, H-1525 Budapest, P.O. Box 49, Hungary — 3Institute for Theoretical Physics, Eötvös University, 1117 Budapest, Pazmany setany 1/a, Hungary
The zero-temperature XX chain is studied with emphasis on the properties of a block of spins inside the chain. We investigate the quantum fluctuations resulting from the entanglement of the block with the rest of the chain using analytical as well as numerical (density matrix renormalization group) methods. It is found that the rest of the chain acts as a thermal environment and an effective temperature can be introduced to describe the fluctuations. We show that the effective temperature description is robust in the sense that several independent definitions (through fluctuation dissipation theorem, comparing with a finite temperature system) yield the same functional form in the limit of large block size. The effective temperature can also be shown to satisfy the basic requirements on how it changes when two bodies of equal or unequal temperatures are brought into contact.