Screening currents in free-field representations of Kac-Moody algebras

In this paper a general procedure is presented whereby screening currents of the vertex type can be constructed from any Kac-Moody algebra in free-field representation. This method is applied to sl(n) and sp(4), where explicit free-field representations for the Kac-Moody algebra are available. In this way the authors obtain for the first time the correct form of the screening currents expressed by infinite series. It is also noted that both the Kac-Moody and the screening currents can be formulated on a lattice, a formalism which can simplify calculations and reveal the intricate structures of these currents