Universal R-matrix and graded Hopf algebra structure of

Abstract

An explicit formula for the universal R-matrix of is given using Drinfeld's basis. Its generators are chosen according to a non-standard set of positive simple roots. The expression implies an extension of the standard graded Hopf algebra defined in terms of its Chevalley generators to . In addition to a four-dimensional vector representation, an infinite-dimensional representation of suitable for the description of a model related to the integer quantum Hall transition is considered.