Research Techniques

Our researches use the most effective methods of condensed matter theory, including the following:

• Diagram technique for Hubbard operators. This analytical method is especially effective in studying the systems with strong electron correlations. An important feature of the diagram technique for Hubbard operators is the presence of terminal diagrams due to the kinematic interaction.
• Non-equilibrium Keldysh diagram technique for Hubbard operators. The theoretical description of electronic structure of strongly correlated systems based on the Keldysh technique allows avoiding certain technical difficulties caused by need for analytical continuation of strength and mass operators. This eliminates the problems related to the analytical properties of Green's functions when taking into account loop diagrams.

We use other well-known approved techniques and approaches, including the transfer matrix method, the method of Bogolyubov canonical u-v-transformations, operator form of the perturbation theory, and the method of irreducible Green's functions with the Zwanzig-Mori projection technique involved.