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.
- 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.
- 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?
- 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 ----------------------------------------
Kruno,
If you want to find transition temperatures then QWL is not the best method in any case. Better do standard finite size scaling using the looper code in all cases.
Matthias
On Oct 30, 2009, at 10:26 AM, Prsa Krunoslav wrote:
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.
- 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.
- 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?
- 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
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