Dresden 2011 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 2: Statistical Physics (general)

DY 2.1: Talk

Monday, March 14, 2011, 10:15–10:30, ZEU 255

A new factorizacion form for the partition function in quantum open systems — •Juan-Diego Urbina and Klaus Richter — Institut für Theoretische Physik, Universität Regensburg, D-93053 Regensburg, Germany

We adress the microscopic description of quantum systems strongly coupled with a linear bath (particularly at very low temperatures) in the framework of the Caldeira-Legget model for the environment. By careful revision of the huge literature on the subject, we support our claim that a weak coupling assumption is inconsistenly done at a very critical stage in basically all thermodynamic calculations. This extra assumption (based on its exactness for harmonic systems) is expressed through a factorized form for the full system-plus-environment equilibrium partition funtion $Z(\beta)$, in terms of the partition function of the bath $Z_{B}(\beta)$ and the effective partition function of the system $Z_{eff}(\beta)$. We will show how the explicit construction of the full partition function of a non-harmonic system (the particle in a box interacting with a bath of harmonic oscilators) suggests a different picture where an extra universal factor, representing neither the system nor the bath but the interaction between them, is naturally added to $Z(\beta)$ .