Dear Prof. Troyer,
Thanks for your answer. Yes, the lattice is 3D; and no, the frustration is not strong.
I will follow your advice then: I'll try the QWL for the non-frustrated case, and with looper add points on the frustrated side of the phase diagram, if that will be feasible.
All the best,
Kruno
> No, the current QWL code cannot do that. It is best to use the looper
> code. Are you talking about 3D lattices? If frustration is strong the
> sign problem will make simulations impossible at T_N.
> Matthias
> On 29 Oct 2009, at 12:20, Prsa Krunoslav wrote:
> Dear ALPS maintainers,
> Since nobody has yet answered to my questions from almost a month
> ago, I will repeat just one question this time.
>
> Can the current incarnation of the QWL code handle frustrated
> lattices? Specifically, I want to find the transition temperature as
> a function T_N(J2/J1), where J2 and J1 are antiferromagnetic.
>
>
> All the best,
> Kruno
>
> ---------------------------------------
> Krunoslav Prsa, Ph. D. Student
> Laboratory for Neutron Scattering
> Paul Scherrer Institute and ETH-Zürich
> CH-5232 Villigen PSI, Switzerland
> tel: +41 56 310 20 91
> mob: +41 76 386 17 99
> ----------------------------------------
>
>
>
> -----Original Message-----
> From: Prsa Krunoslav
> Sent: Friday, October 02, 2009 2:56 PM
> To: comp-phys-alps-users at phys.ethz.ch
> Subject: Quantum Wang-Landau algorithm question: applicability of
> QWL on (slightly) frustrated lattices
>
>
> Dear ALPS maintainers,
>
> I have three questions with regards to your extremely powerful QWL
> algorithm.
>
> 1. In the ALPS online documentation section for QWL algorithm there
> is a note:
> "Note: This first version allows the simulation of isotropic
> Heisenberg spin-1/2 ferro- and antiferromagnetic models on arbitrary
> non-frustrated lattices at zero magnetic field. In the future, we
> plan to relax this constraint, and also provide an implementation of
> the QWL perturbation expansion. "
>
> Has this been improved with regards to antiferro- frustrated
> lattices? I am using ALPS version 1.3.3.
>
> 2. When I run the qwl for my slightly frustrated S=1/2 3D lattice
> (consisting of triangular antiferro patterns J1-J1-J2 with J2~0.15
> J1) the program does not seem to complain (It does not seem to
> complain even for the triangular lattice). Can its output for this
> situation be trusted though?
>
> 3. I was also wondering if I can generally verify the results (say
> T_N) of the frustrated model by an extrapolation from the non-
> frustrated side (say ferro J2=-0.5,...,-0.1,0), thereby assuming a
> mean-field like behaviour T_N~(J1-J2), for small J2. I am an
> experimentalist so I may not be aware of this. Is there a general
> result that would say it's not possible or at least a counterexample?
>
> It may be of relevance to some of the questions that in this lattice
> there is a change in the classical ground state from Neel to the
> triangular at J2=J1/3.
>
> All the best,
> Kruno
>
> ---------------------------------------
> Krunoslav Prsa, Ph. D. Student
> Laboratory for Neutron Scattering
> Paul Scherrer Institute and ETH-Zürich
> CH-5232 Villigen PSI, Switzerland
> tel: +41 56 310 20 91
> mob: +41 76 386 17 99
> ----------------------------------------
---------------------------------------
Krunoslav Prsa, Ph. D. Student
Laboratory for Neutron Scattering
Paul Scherrer Institute and ETH-Zürich
CH-5232 Villigen PSI, Switzerland
tel: +41 56 310 20 91
mob: +41 76 386 17 99
----------------------------------------