Functional integration is one of the most powerful methods of contempo-
rary theoretical physics, enabling us to simplify, accelerate, and make
clearer the process of the theoretician's analytical work. Interest in
this method and the endeavour to master it creatively grows incessantly.
This book presents a study of the application of functional integration
methods to a wide range of contemporary theoretical physics problems.
The concept of a functional integral is introduced as a method of
quantizing finite-dimensional mechanical systems, as an alternative to
ordinary quantum mechanics. The problems of systems quantization with
constraints and the manifolds quantization are presented here for the
first time in a monograph. The application of the functional integration
methods to systems with an infinite number of degrees of freedom allows
one to uniquely introduce and formulate the diagram perturbation theory
in quantum field theory and statistical physics. This approach is
significantly simpler than the widely accepted method using an operator
approach.