[ALPS-users] Questions about MC Simulation of XY Model

Hi,

I am just new to ALPS, and I have a silly question about running MC simulations of XY model:

Following the tutorials, I use python to run the simulations and change the model from “Ising” to “XY”, like:

import pyalps

parms = [ { 'LATTICE': "square lattice", 'T': 1, 'J': 1, 'THERMALIZATION': 10000, 'SWEEPS': 400000, 'UPDATE': "cluster", 'MODEL': "XY", 'L': 8 } ]

input_file = pyalps.writeInputFiles('data/parmXY', parms) pyalps.runApplication('spinmc', input_file, Tmin=5) result_files = pyalps.getResultFiles(prefix='data/parmXY')

data = pyalps.loadMeasurements(result_files)

how can I get some observables like <\cos\theta>, where \theta is the direction of the spin at each site? If such a quantity is not provided directly by ALPS, is there a possible method to get these quantities I want. I just get lost when I see the source code of ALPS.

Thank you in advance!

Best, Wei