  In hep-th/0010293 Kapustin and Orlov introduce the notion of an OPE-algebra
and propose that it formalizes conformal field theories in the same way as
vertex algebras formalize chiral algebras, i.e. the subalgebras of holomorphic
fields of conformal field theories. In this thesis we study the question which
concepts and results of the general theory of vertex algebras can be extended
to OPE-algebras.
