Hi,
We have recently installed the ALPS code, downloaded from the links on
the Wiki. We are using version 1.3.2 of the libraries and applications.
The install went smoothly, and the tests worked fine. We have both
Cygwin and Ubuntu installs and the problems. We successfully ran some
spin models with qmc, dmrg, and exact diagonalization. However, we
attempted to run some DMRG calculations with a fermion Hubbard model, and
this was unsuccesful. We used a periodic boundary condition chain lattice
and a non-interacting system to start with, and use the default
"models.xml" and "lattices.xml" that came with the packages. Our input
file was
---- BEGIN INPUT FILE, parm-fermion.xml ----
LATTICE="chain lattice"
SWEEPS=4
MAXSTATES=26
CONSERVED_QUANTUMNUMBERS="Nup,Ndown"
{
MODEL="fermion Hubbard", L=10, Nup_total=1, Ndown_total=1
mu=1.0
t=1.0
U=0
NUMBER_EIGENVALUES=1
MEASURE_LOCAL[local spin up density]=n_up
MEASURE_CORRELATIONS[up up Green function]="cdag_up:c_up"
MEASURE_CORRELATIONS[up down Green function]="cdag_up:c_down"
MEASURE_CORRELATIONS[down down Green function]="cdag_down:c_down"
MEASURE_CORRELATIONS[up density up density correlation function]=n_up
MEASURE_CORRELATIONS[down density down density correlation
function]=n_down
MEASURE_CORRELATIONS[up density down density correlation
function]="n_up:n_down"
}
---- END INPUT FILE ----
When we run this ("parameter2xml parm-fermion" then "dmrg
parm-fermion.in.xml"), though the energy appears to be correct, we (1)
obtain correlation functions which are completely different than the
expected result (often coming out to be zero) and (2) most of the
site-to-site correlations (e.g., site i to site j, with i not equal to
zero) are missing. A symptom may be provided by the (stderr?) output of
the code: "Did not get the right number of measurements". The problem is
independent of the SWEEPS and MAXSTATES used. If we run the exact
diagonalization code "sparsediag", however, we obtain the expected
results. So it seems we are setting up something incorrectly with the
dmrg input.
To further examine the problem, we re-ran with open boundary conditions
(just changing "chain lattice" into "open chain lattice" in the file
above). Although now the right number of measurements appear to be taken
and the right correlation function elements are non-zero, the results
still disagree with our expectations and exact diagonalization.
Finally, we obtain similar problems with bosons. Spin models, however,
work without problem and agree with exact diagonalization.
We have not included the output files since they are somewhat lengthy
and should be reproducible, but if it would help we would be happy to send
them.
Thanks for any help and the wonderful program!
Kaden and Stefan