On 9 Jul 2008, at 21:24, Brian Keith wrote:

Hello professor Troyer,

                                 I am trying to use ALPS to  

study a magnetic heisenberg ladder with anti-fm interactions in the rail direction and ferromagnetic interactions in the rung direction. I believed it would be easy to simulate if I set J_rung= 1 and J_rail= -1 but I get the same MvT results whether I do it this way or make it a uniform ladder. Is changing the sign the correct way to simulate ferromagnetic interactions?

thanks for your help, Brian

Hi Brian,

Do you use the classical or the QMC codes? If you use the QMC codes like in the tutorial then the couplings are J and J' and not J_rail and J_rung. Or do you define your own model file? If so then please send your input files and we can help

Matthias Troyer