The one-particle Green functions for strongly correlated finite Fermi systems

А. К. Власников, Artem Lunev, V. M. Mikhailov

The single-particle Green function formalism (Gor’kov’s method) is applied to calculate the energies of finite superconducting Fermi systems with a finite number of particles. It is shown that strong pairing leads to equations similar to those from the Bardeen-Cooper-Schrieffer theory.

M. K. Weigel

M. Bönitz, Niclas Schlünzen, S. Hermanns

Abstract Transport properties of strongly correlated quantum systems are of central interest in condensed matter, ultracold atoms and in dense plasmas. There, the proper treatment of strong correlations poses a great challenge to theory. Here, we apply a Nonequilibrium Green Functions approach using a lattice model as a basic system. This allow us to treat a finite spatially inhomogeneous system with an arbitrary nonequilibrium initial state. Placing all particles initially to one side of the system allows for a nonequilibrium study of diffusion. Strong correlation effects are incorporated via T‐matrix selfenergies. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Donald H. Kobe, Warren B. Cheston

S K Sarker

A new functional integral mapping of a strongly correlated Fermi system to another Fermi system is presented. The strong correlations appear in the new system through momentum- and frequency-dependent coupling constants characterising correlated multi-particle motions, which can be treated perturbatively. The method is well suited to treat Hubbard and Anderson models. For the Hubbard model, the lowest-order term reproduces Hubbard's two-band Green function. Second-order processes leading to spin fluctuations are identified.