YANGIAN DOUBLE

Studying the algebraic structure of the double DY(g) of the Yangian Y( g), we present the triangular decomposition of DY(g) and a factorizati on for the canonical pairing of the Yangian with its dual inside Y-o(g ). As a consequence, we describe a structure of the universal R-matrix R for DY(g) which is complete for DY(sl(2)). We demonstrate how this formula works in evaluation representations of Y(sl(2)). We interpret the one-dimensional factor arising in concrete representations of R as a bilinear form on highest-weight polynomials of irreducible represen tations of Y(g) and express this form in terms of Gamma-functions.