[ALPS-users] Local measurements and correlations with sparsediag

Dear all,

I would like to study one-site and two-sites correlation functions in certain variants of the 1D Hubbard model.

I have tried to compute the local densities (total, up and down) in a small Hubbard chain (10 sites) with open boundary conditions, so that the one-point observables are non-trivial. However, all the local observables return the value 0. The same happens if I try to compute the correlation cdag_up:c_up (or down). The input file is as follows:

MODEL="fermion Hubbard"; LATTICE="open chain lattice"; LATTICE_LIBRARY="./lattices.xml"; MODEL_LIBRARY="./models.xml"; CONSERVED_QUANTUMNUMBERS="Nup; Ndown"; MEASURE_LOCAL[nup]=n_up MEASURE_LOCAL[ndown]=n_down MEASURE_LOCAL[ntot]=n MEASURE_CORRELATIONS[c+up_cup]="cdag_up:c_up" MEASURE_CORRELATIONS[c+dn_cdn]="cdag_down:c_down" U=1; {L=10;Nup_total=3;Ndown_total=3}

Is there a reason why the correlations are not properly computed and/or a mistake in the input file?

Thanks for your time. Cristian