Abstract:
We show that cluster algorithms for quantum models have a
meaning independent of the basis chosen to construct them.
Using this idea, we propose a new method for measuring with
little effort a whole class of Green's functions, once a
cluster algorithm for the partition function has been
constructed. To explain the idea, we consider the quantum XY
model and compute its two point Green's function in various
ways, showing that all of them are equivalent. We also
provide numerical evidence confirming the analytic
arguments. Similar techniques are applicable to other
models. In particular, in the recently constructed quantum
link models, the new technique allows us to construct
improved estimators for Wilson loops and may lead to a very
precise determination of the glueball spectrum.