Variational principle of Bogoliubov and generalized mean fields in many-particle interacting systems (Q2794684)

The paper reviews various approaches to the theory of many-particle interacting systems using the Bogoliubov variational principle for the free energy. The author discusses some of the main principles which are at the basis of the physical and the mathematical background of the variational approach, and he tries to exhibit connections between the variational technique on the one hand, and other methods in the theory of the many-body problem. The following topics are presented: Helmholtz free energy and statistical thermodynamics, calculation of the Helmholtz free energy, mean field, broken symmetry, Bogoliubov variational principle and its application.