Condensed Matter Physics, 2006, vol. 9, No. 3(47), p. 557567, English
DOI:10.5488/CMP.9.3.557
Title:
Nonperturbative construction of the LuttingerWard functional
Author(s):
 M.Potthoff
(Institut für Theoretische Physik und Astrophysik,
Universität Würzburg, Am Hubland, D97074 Würzburg,
Germany)

For a system of correlated electrons, the LuttingerWard
functional provides a link between static thermodynamic quantities
on the one hand and singleparticle excitations on the other. The
functional is useful in deriving several general properties of the
system as well as in formulating the thermodynamically consistent
approximations. Its original construction, however, is
perturbative as it is based on the weakcoupling skeletondiagram
expansion. Here, it is shown that the LuttingerWard functional
can be derived within a general functionalintegral approach. This
alternative and nonperturbative approach stresses the fact that
the LuttingerWard functional is universal for a large class of
models.
Key words:
PLuttingerWard functional, conserving approximations,
diagrammatic perturbation theory, functionalintegral approach,
dynamical meanfield theory,
selfenergyfunctional theory
PACS:
71.10.w, 71.15.m
