This book introduces systematically the operator method for the solution of the Schrödinger
equation. This method permits to describe the states of quantum systems in the entire range of
parameters of Hamiltonian with a predefined accuracy. The operator method is unique compared
with other non-perturbative methods due to its ability to deliver in zeroth approximation the
uniformly suitable estimate for both ground and excited states of quantum system. The method
has been generalized for the application to quantum statistics and quantum field theory. In
this book the numerous applications of operator method for various physical systems are
demonstrated. Simple models are used to illustrate the basic principles of the method which are
further used for the solution of complex problems of quantum theory for many-particle systems.
The results obtained are supplemented by numerical calculations presented as tables and
figures.
