Tetrahedron Equation and Quantum R Matrices for Modular Double of Uq(D(2) n+1), Uq(A(2) 2n) and Uq(C(1) n)

We introduce a homomorphism from the quantum affine algebras Uq(D(2) n+1), Uq(A(2) 2n), Uq(C(1) n) to the n-fold tensor product of the q-oscillator algebra Aq. Their action commutes with the solutions of the Yang–Baxter equation obtained by reducing the solutions of the tetrahedron equation associated with the modular and the Fock representations of Aq. In the former case, the commutativity is enhanced to the modular double of these quantum affine algebras.