In several proofs from the theory of finite-dimensional Lie algebras, an
essential contribution comes from the Jordan canonical structure of
linear maps acting on finite-dimensional vector spaces. On the other
hand, there exist classical results concerning Lie algebras which advise
us to use infinite-dimensional vector spaces as well. For example, the
classical Lie Theorem asserts that all finite-dimensional irreducible
representations of solvable Lie algebras are one-dimensional. Hence,
from this point of view, the solvable Lie algebras cannot be
distinguished from one another, that is, they cannot be classified. Even
this example alone urges the infinite-dimensional vector spaces to
appear on the stage. But the structure of linear maps on such a space is
too little understood; for these linear maps one cannot speak about
something like the Jordan canonical structure of matrices. Fortunately
there exists a large class of linear maps on vector spaces of arbi-
trary dimension, having some common features with the matrices. We mean
the bounded linear operators on a complex Banach space. Certain types of
bounded operators (such as the Dunford spectral, Foia§ decomposable,
scalar generalized or Colojoara spectral generalized operators) actually
even enjoy a kind of Jordan decomposition theorem. One of the aims of
the present book is to expound the most important results obtained until
now by using bounded operators in the study of Lie algebras.