Leipzig 2002 – wissenschaftliches Programm

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MP: Theoretische und Mathematische Grundlagen der Physik

MP 13: Quantenfeldtheorie: Renormierungs-Gruppen Methoden u.ä.

MP 13.1: Fachvortrag

Montag, 18. März 2002, 14:00–14:20, HS 18

Recursive Variational Calculation of the Imaginary-Time Evolution Amplitude — •Florian Weißbach, Axel Pelster, and Hagen Kleinert — Freie Universität Berlin, Institut für Theoretische Physik, Arnimallee 14, 14195 Berlin

We present a perturbative calculation of the quantum statistical imaginary-time evolution amplitude of the anharmonic oscillator. For this purpose we solve the corresponding Schrödinger equation by performing a double expansion with respect to both the coupling strength and the coordinate. By recursively solving the resulting set of coupled ordinary differential equations we can go to much higher orders than in a Feynman diagrammatic approach. Using these expansions we perturbatively evaluate the free energy, the density matrix, and the 2-point correlation function of the anharmonic oscillator. Applying variational perturbation theory we determine these quantities for all values of the coupling strength and the temperature.