Flow Equations and Normal Ordering. A Survey
arXiv:cond-mat/0511660 · doi:10.1088/0305-4470/39/25/S29
Abstract
First we give an introduction to the method of diagonalizing or block-diagonalizing continuously a Hamiltonian and explain how this procedure can be used to analyze the two-dimensional Hubbard model. Then we give a short survey on applications of this flow equation on other models. Finally we outline, how symmetry breaking can be introduced by means of a symmetry breaking of the normal ordering, not of the Hamiltonian.
11 pages, contribution to the workshop on the Renormalization Group, Helsinki 2005