SLAVE-BOSON THEORIES OF CORRELATED ELECTRON-SYSTEMS

Slave bosom theories of various models of correlated fermions are crit ically reviewed and several new results are presented. In the example of the Anderson impurity model the limitations of slave boson mean fie ld theory are discussed. Self-consistent conserving approximations are compared with results obtained from the numerical renormalization gro up. The gauge field theory of the t-J-model is considered in the quasi static approximation. It is shown that weak localization effects can g ive valuable information on the existence of gauge fields. Application s of the slave-boson approach due to Kotliar tliar and Ruckenstein to the Hubbard model are also discussed.