Reviews basic concepts such as the measure, the integral, Banach spaces, bounded operators and generalized functions of functional analysis. This work covers topics including unbounded operators, spectral decomposition, expansion in generalized eigenvectors, rigged spaces and partial differential operators.

First works related to the topics covered in this book belong to J. Delsarte and B. M. Le vitan and appeared since 1938. In these works, the families of operators that generalize usual translation operators were investigated and the corresponding harmonic analysis was constructed. Later, starting from 1950, it was noticed that, in such constructions, an important role is played by the fact that the kernels of the corresponding convolutions of functions are nonnegative and by the properties of the normed algebras generated by these convolutions. That was the way the notion of hypercomplex...

This two-volume work is devoted to the methods of the spectral theory of operators and the important role they play in infinite-dimensional analysis and its applications. Central to this study is the theory of the expansion of general eigenfunctions for families of commuting self-adjoint or normal operators. This allows a consideration of commutative models which can be applied to the representation of various commutation relations.