Regensburg 2007 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 30: Poster II

DY 30.32: Poster

Donnerstag, 29. März 2007, 16:00–18:00, Poster D

Continuous time cluster Monte Carlo algorithm for the spin-boson model — •Andre Winter and Heiko Rieger — Theoretische Physik, Universität des Saarlandes, PF 151150, D-66041 Saarbrücken

A Monte Carlo algorithm to explore the quantum phase transition between localized and delocalized phase of the sub-Ohmic spin-boson model is presented. Its partition function can be written as a path integral over spin-worldlines in imaginary time involving an effective action that contains long-range interaction between spin values at different times. This path integral is evaluated with a continuous (imaginary) time Monte-Carlo algorithm with cluster updates. In this way the usual Trotter-discretization is avoided and results of simulations using this algorithm are expected to be representative for the spin-boson model also in the sub-Ohmic regime. We compute the critical exponents of the phase transition and their dependence on the bath exponent characterizing the low frequency behavoir of the spectral function of the bosonic bath.