Two-parameter quantum groups and R-matrices: classical types

We construct finite R-matrices for the first fundamental representation V of two-parameter quantum groups Ur,s(g) for classical g, both through the decomposition of V⊗ V into irreducibles Ur,s(g)-submodules as well as by evaluating the universal R-matrix. The latter is crucially based on the construction of dual PBW-type bases of U±r,s(g) consisting of the ordered products of quantum root vectors defined via $(r,s)$-bracketings and combinatorics of standard Lyndon words. We further derive explicit formulas for affine R-matrices, both through the Yang-Baxterization technique of [M.Ge, Y.Wu, K.Xue, "Explicit trigonometric Yang-Baxterization", Internat. J. Modern Phys. A 6 (1991), no.21, 3735-3779] and as the unique intertwiner between the tensor product of $V(u)$ and $V(v)$, viewed as modules over two-parameter quantum affine algebras Ur,s(g) for classical g. The latter generalizes the formulas of [M.Jimbo, "Quantum R matrix for the generalized Toda system", Comm. Math. Phys. 102 (1986), no. 4, 537-547] for one-parametric quantum affine algebras.