THERMODYNAMIC LIMIT OF DENSITY-MATRIX RENORMALIZATION

The density matrix renormalization group discovered by White is invest igated. In the case where renormalization eventually converges to a fi xed point we show that quantum states in the thermodynamic limit with periodic boundary conditions can be simply represented by a ''matrix p roduct ground state'' with a natural description of Bloch states of el ementary excitations. We then observe that these states can be rederiv ed through a simple variational ansatz making no reference to a renorm alization construction. The method is tested on the spin-1 Heisenberg model.