There is no question that the cohomology of infinite- dimensional Lie
algebras deserves a brief and separate mono- graph. This subject is not
cover d by any of the tradition- al branches of mathematics and is
characterized by relative- ly elementary proofs and varied application.
Moreover, the subject matter is widely scattered in various research
papers or exists only in verbal form. The theory of infinite-dimensional
Lie algebras differs markedly from the theory of finite-dimensional Lie
algebras in that the latter possesses powerful classification theo-
rems, which usually allow one to "recognize" any finite- dimensional Lie
algebra (over the field of complex or real numbers), i.e., find it in
some list. There are classifica- tion theorems in the theory of
infinite-dimensional Lie al- gebras as well, but they are encumbered by
strong restric- tions of a technical character. These theorems are
useful mainly because they yield a considerable supply of interest- ing
examples. We begin with a list of such examples, and further direct our
main efforts to their study.