LAX PAIR FORMULATION FOR ONE-DIMENSIONAL HUBBARD OPEN-CHAIN WITH CHEMICAL-POTENTIAL

The Lax pair for the one-dimensional Hubbard spin chain with open boun dary conditions (BC) is explicitly constructed and two different kinds of boundary K-matrices compatible with the integrability of the model are obtained. Our construction provides an alternative and direct dem onstration for the quantum integrability of the model and it is found that the model is related to a class of commuting transfer matrices of an equivalent coupled asymmetric six-vertex model with open BC. Our r esults show that the chemical potential term is indeed nontrivial for the underlying algebraic structure of the model.