ANALYTIC FORMULATIONS OF THE DENSITY-MATRIX RENORMALIZATION-GROUP

We present two new analytic formulations of the density matrix renorma lization group (DMRG) method. In these formulations we combine the blo ck renormalization group (BRG) procedure with the variational and Fokk er-Planck methods. The BRG method is used to reduce the lattice size w hile the latter are used to construct approximate target states to com pute the block density matrix. We apply our DMRG methods to the Ising model in a transverse field (ITF model) and compute several of its cri tical properties, which are then compared with the old BRG results.