HUBBARD-MODEL WITH LUSCHER FERMIONS

We study the basic features of the two-dimensional quantum Hubbard mod el at half-filling by means of the Luscher algorithm and the algorithm based on direct update of the determinant of the fermionic matrix, We implement the Luscher idea employing the transfer matrix formalism wh ich allows to formulate the problem on the lattice in (2 + 1) dimensio ns. We discuss the numerical complexity of the Luscher technique, syst ematic errors introduced by a polynomial approximation and introduce s ome improvements which reduce long autocorrelations, In particular we show that preconditioning of the fermionic matrix speeds up the algori thm and extends the available range of parameters. We investigate the magnetic and the one-particle properties of the Hubbard model at half- filling and show that they are in qualitative agreement with the exist ing Monte Carlo data and the mean-field predictions, (C) 1998 Elsevier Science B.V.