Numerical stability and the sign problem in the determinant quantum Monte Carlo method
A recent paper by Matuttis and Ito questions the numerical accuracy of a widely-used fermion Monte Carlo algorithm. They also claim that the increase in the d-wave pairfield susceptibility chi(d)(T) of a doped 4 x 4 Hubbard model at low temperature, previously found using this algorithm, is an artifact due to numerical errors. Here, we provide tests which show that this algorithm is numerically accurate and show that the simulation of chi(d) for a 2 x 2 lattice agrees with exact diagonalization results. We also provide more complete data for chi(d) on a 4 x 4 lattice that is consistent with our previous results.
sign problem quantum monte carlo hubbard model high temperature superconductivity