Functional Integrals for Correlated Fermions
Abstract
Functional integral methods provide a way to define mean--field theories and to systematically improve them. For the Hubbard model and similar strong--correlation problems, methods based in particular on the Hubbard--Stratonovich transformation have however been plagued by difficulties to formulate the problem in a spin--rotation invariant way. Here a formalism circumventing this problem by using a space-- and time--dependent spin reference axis is discussed. This formulation is then used to suggest a possible alternative to Nagaoka ferromagnetism in the strongly correlated Hubbard model in the vicinity of half--filling. Finally, some aspects of single--particle spectra in a simplified model for a short--range ordered antiferromagnet are discussed.
Cite
@article{arxiv.cond-mat/9411059,
title = {Functional Integrals for Correlated Fermions},
author = {H. J. Schulz},
journal= {arXiv preprint arXiv:cond-mat/9411059},
year = {2009}
}
Comments
10 pages, LaTeX2e, 3 postscript figures appended via uufiles