Also, you can use "alternative fermion Hubbard" instead of "fermion Hubbard" and define Sz_total and N_total because they are defined as quantum numbers in that model. It appeared to work for me. By the way, there isn't any difference between the "anistropic square lattice" and the "square lattice" with what you are doing. The anisotropic square lattice allows for different bond parameters and such in the horizontal and vertical directions, but you haven't defined those so the two lattices are the same. Both have periodic boundary conditions. If you want open boundary conditions you should use "open ladder". I hope that helps. ________________________________________ From: comp-phys-alps-users-bounces@phys.ethz.ch [comp-phys-alps-users-bounces@phys.ethz.ch] On Behalf Of Matthias Troyer [troyer@phys.ethz.ch] Sent: Sunday, April 19, 2009 11:47 AM To: comp-phys-alps-users@phys.ethz.ch Subject: Re: [ALPS-users] 3 particles with 0.5 total spin

Have you tried setting the Nup_total and Ndown_total ? The quantum numbers are Nup and Ndown

Matthias

On 17 Apr 2009, at 13:23, khalid hassan wrote:

Dear Sir

I am not able to calculate the energy states for the fermionic hubbard model for 2 by 2 plaquette for 3 particles total spin S=0.5

Actually for 3 particles the total spin comes out to be 1.5 as measured by MEASURE_AVERAGE[Magnetization]="Sz" command

I need the energies for the model described above. please write a program for me.

I am very upset as I tried all the combinations I think and get the same input. Thats why this is third mail from me in this day.

Best Regards Khalid Loane