Computer aided perturbation theory by cumulants: dimerized and frustrated spin 1/2 chain

Abstract

This paper demonstrates that a computer aided perturbation theory can easily be realized by use of a cumulant approach. In contrast to a recent alternative formulation on the basis of Wegner's flow equation method the present approach can be applied to systems with arbitrary Hilbert space. In particular an equidistant spectrum of the unperturbed part of the Hamiltonian is not needed. The method is illustrated in detail for dimerized and frustrated spin 1/2 chains for which the ground state energy is calculated up to seventh order perturbation theory.

arXiv comment6 pages including 1 table, submitted to Phys. Rev. B

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• Perturbation Theory by Flow Equations: Dimerized and Frustrated S=1/2 Chain
• Study of the magnetic susceptibility in the spin-Peierls system CuGeO${}_3$
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Cited by in corpus (2)

• Flow Equations and Normal Ordering. A Survey
• DMRG study of scaling exponents in spin-1/2 Heisenberg chains with dimerization and frustration