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 ----------------------------------------