Interplay between a quantum impurity and a boundary field in the SUSY t-J model

We study the role of bound states appearing in different formulations of the Bethe ansatz for the supersymmetric t-J model with a boundary potential and an integrable impurity. For special values of the parameters describing the boundary and the impurity the charge fluctuations at the latter vanish. The population of the bound states selects different sectors of the impurity levels leading to integrable Kondo impurities.