Ruprecht-Karls-Universität Heidelberg
University of HeidelbergFaculty of Physics and AstronomyInstitut of Theoretical PhysicsAndreas MielkeAndreas Mielkeemail

Andreas Mielke
Institut for Theoretical Physics
Ruprecht-Karls University
Philosophenweg 19
D-69120 Heidelberg
Germany
Tel.: ++49 6221 549431 (Secretary)
Fax: ++49 6221 549331
e-mail: mielke@tphys.uni-heidelberg.de


Tobias Stauber, Andreas Mielke: Flow equations for Hamiltonians: Contrasting different approaches by using a numerically solvable model
J. Phys. A36, 2707-2736 (2003) .

Archiv: cond-mat/0209643

Abstract

To contrast different generators for flow equations for Hamiltonians and to discuss the dependence of physical quantities on unitarily equivalent, but effectively different initial Hamiltonians, a numerically solvable model is considered which is structurally similar to impurity models. By this we discuss the question of optimization for the first time. A general truncation scheme is established that produces good results for the Hamiltonian flow as well as for the operator flow. Nevertheless, it is also pointed out that a systematic and feasible scheme for the operator flow on the operator level is missing. For this, an explicit analysis of the operator flow is given for the first time. We observe that truncation of the series of the observable flow after the linear or bilinear terms does not yield satisfactory results for the entire parameter regime as - especially close to resonances - even high orders of the exact series expansion carry considerable weight.

BibTeX-entry

@article{Stauber2002a,
author="Tobias Stauber, Andreas Mielke",
title="Flow equations for Hamiltonians: Contrasting different approaches by using a numerically solvable model",
journal="J. Phys. A",
volume="36",
pages="2707-2736",
year="2003"
}

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Last changes: 15.11.2017. mielke@tphys.uni-heidelberg.de