Title: Non-perturbative construction of the Luttinger-Ward functional
Author(s):

M.Potthoff (Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany)

For a system of correlated electrons, the Luttinger-Ward functional provides a link between static thermodynamic quantities on the one hand and single-particle 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 weak-coupling skeleton-diagram expansion. Here, it is shown that the Luttinger-Ward functional can be derived within a general functional-integral approach. This alternative and non-perturbative approach stresses the fact that the Luttinger-Ward functional is universal for a large class of models.

Key words: PLuttinger-Ward functional, conserving approximations, diagrammatic perturbation theory, functional-integral approach, dynamical mean-field theory, self-energy-functional theory

PACS: 71.10.-w, 71.15.-m