Hello All,
coould someone more experienced than me could explain briefly what type of measurements (averages of observables) may be extracted from current version. I am most interested in boson model now but question is more general. The section on parameters/measurements is unfortunately missing in wiki...
Example:
MEASURE_LOCAL[Local density]=n
allows to get occupation of sites <n_i> for Bose-Hubbard. (Thanks, Akin, for this example). Probably other averages can be extracted but how?
I tired a second moment by typing simply
MEASURE_LOCAL[Local density^2]=n2
that for sparse/full diagonalization gives (e.g. sparse) Cannot evaluate expression n2(i)
similarly for MEASURE_LOCAL[Compressibility]=kappa
[actually in one of the files kappa(i) seems to be evaluated as it should from n2(i) and n(i) ]
Worm algorithm in QMC yields:
Will not measure "Compressibility" since it is off-diagonal or not a site operator Will not measure "Local density^2" since it is off-diagonal or not a site operator
(which are apparently incorrect comments anyway)
anybody kind enough to help?
Best wishes kuba