Beginning with an introduction to the T-product approach in the theory of a particle interacting with bosonic fields as applied, for example, to the linearized polaron model, the book goes on to deal with the equilibrium state objective being to derive Bogolubov's inequality for the reduced free energy of the polaron. The third chapter deals with some problems related to the non-equilibrium polaron theory, including polaron kinetics. Finally, alternative methods used in polaron theory are also presented and compared with Bogolubov's method.

Analyzes the possibility of reduction of the full polaron Hamiltonian to the linear one, and introduces a special method of calculating thermodynamical characteristics based on the calculation of the averages of T-products.

Useful as an advanced textbook by graduate students, even ambitious undergraduates in physics, this title is also suitable for non experts in physics who wish to have an overview of some of the classic and fundamental quantum models in the subject. It includes material needed to dwell further into the subject and explore the research literature.

Useful as an advanced textbook by graduate students, even ambitious undergraduates in physics, this title is also suitable for non experts in physics who wish to have an overview of some of the classic and fundamental quantum models in the subject. It includes material needed to dwell further into the subject and explore the research literature.