Dear Matthias,

thank you for your reply. I'd have one more question: when you say "no, not yet but this could be added." do you mean that I cannot measure helicity modulus without dealing with Python/C++/whatever or that I cannot measure helicity modulus at all in the current version of ALPS?

Best Regards, Alvise

Dear Alvise,

FYI, the looper QMC code in the present version of ALPS can calculate the helicity modulus (or stiffness) for the quantum version of 3D XY model.

Best, Synge

On 2012/07/02, at 4:26, Matthias Troyer wrote:

Right, we need to add it to the C++ code.

Matthias

On Jul 1, 2012, at 6:29 PM, Alvise Scarpa wrote:

...

Dear Matthias,

thank you for your reply. I'd have one more question: when you say "no, not yet but this could be added." do you mean that I cannot measure helicity modulus without dealing with Python/C++/whatever or that I cannot measure helicity modulus at all in the current version of ALPS?

Best Regards, Alvise

Thanks Rachele, that's very useful to me!

Regards, Alvise

2012/7/1 Rachele Nerattini r.nerattini@gmail.com

Dear Alvise,

I'm using ALPS to simulate three-dimensional Ising, XY and Heisenberg models. I've never studied the helicity modulus but if you need it I can copy and paste here after the input file I use to run my simulations. While you waiting for the help of someone more expert then me, you can use it to run a simulations on your own and see if in the results you'll get you'll find something useful for your purposes... Good work and all the best Rachele Nerattini

LATTICE="simple cubic lattice" T=2.20167 J=1 THERMALIZATION=200000 SWEEPS=1000000 UPDATE="cluster" MODEL="XY" BOUNDARY type="periodic" S=1 {L=10;}

This is the input file you need to simulate the classical XY model defined on a three dimensional lattice of edge 10 (total number of spins = 10*10*10). You can change the number of thermalization and sweeps steps as you prefer. The model has been simulated at the critical temperature and I used the cluster algorithm to perform the simulation. If you need to simulate a given lattice for different values of the temperature you can do the following:

LATTICE="simple cubic lattice" L=10; J=1 THERMALIZATION=200000 SWEEPS=1000000 UPDATE="cluster" MODEL="XY" BOUNDARY type="periodic" S=1 {T=1.5; T=2.0; T=2.20167; T=3.0; T=...?} The values of the parameters that you give out of braces hold for every simulations, those which are in braces are tipical of a particular simulation.

2012/7/1 Alvise Scarpa scalvis@gmail.com

...

Hi,

I'd need to simulate a three-dimensional XY model, studying the helicity modulus as a function of temperature. (3D XY means that the sites are defined on a cubic lattice, while the spins are constrained on a plane)

I'd have a few questions:

0. Can I do that with ALPS? (I suppose the answer will be yes...)
1. Is it possible to do that just from a parameter file, without using

the Python interface? In particular, how is it possibile to measure the helicity modulus? 2) Is there any place where I could find a relevant parameter file, or one I could adapt to fit my needs?

Thanks in advance (and sorry if the question is too silly, I have been playing with ALPS for a couple of days so far! I have searched for my issues in the documentation by I could not find relevant examples!)

Best Regards, Alvise