Hi Mattias,

By anisotropic model on a ladder I mean that we have two different interaction terms in Hamiltonian as shown in the file attached. Thus we have two bond types "0" and "1" in horizontal and vertical directions and we want to have different interaction terms in horizontal and vertical directions.


As far as I understand, according to "spin" model definition J0 parameter should be for bond type="0" and J1 for bonds type="1".

If we set J=1 only then (even if J1=0) all bonds irrespective of their type should get 1 as bond term, don't you?

In the case we specify J0=1 and J1=1 again all bonds should get 1 as bond term and the model results should be the same
as for setting J only. In this case both isotropic and anisotropic models should give similar results.

Am I  missed something?

Regards,
Ruben


From: Matthias Troyer <troyer@phys.ethz.ch>
To: comp-phys-alps-users@lists.phys.ethz.ch
Sent: Mon, December 20, 2010 11:39:53 AM
Subject: Re: [ALPS-users] anisotropic Heisenberg model setup


On Dec 20, 2010, at 2:47 PM, Ruben Ghulghazaryan wrote:

Dear Mattias,

Thank you very much for your letter.
Please find my questions and comments below.

Thank you in advance, 
Ruben

From: Matthias Troyer <troyer@phys.ethz.ch>
To: comp-phys-alps-users@lists.phys.ethz.ch
Sent: Sat, December 18, 2010 1:06:54 PM
Subject: Re: [ALPS-users] anisotropic Heisenberg model setup


On Dec 18, 2010, at 5:02 PM, Ruben Ghulghazaryan wrote:

> Hi Mattias,
> 
> Should i use Jz=1, Jxy=1 and  Jz0=1, Jxy0=1, Jz1=1, Jxy1=1 setting for my experiment?

This would be isotropic and not anisotropic.

---> That's correct. This is why, we should  expect that the results of simulations be absolutely the same for fulldiag program. But simulations show different results for 
Jz=1, Jxy=1 and  Jz0=1, Jxy0=1, Jz1=1, Jxy1=1 settings. That is confusing.

That is because as I said, J=J0 but not J1, thus if you set only J, the J1 terms will all be zero.

I want to make sure that anisotropic program works as expected that is why I want to make this experiment and check whether anisotropic model 
with the same settings for different bond types and isotropic model with the same interaction bond term give same results.
My tests show that the results are not the same and this may be an indication of a problem with program or miss usage from my side.

What do you mean by "isotropic model" and "anisotropic model"?

Matthias