Structure of Lorentzian algebras and Conformal Field Theory
  The main properties of indefinite Kac-Moody and Borcherds algebras, considered in a unified way as Lorentzian algebras, are reviewed. The connection with the conformal field theory of the vertex operator construction is discussed. By the folding procedure a class of subalgebras is obtained. 
V. Marotta and A. Sciarrino