Are you aware that you use periodic and not open boundary conditions here? To look at a single plaquette please use at open boundary conditions. Also, for the fermion Hubbard model the quantum numbers, if you look at the model file are Nup and Ndown and not N and Sz.

Matthias

On 17 Apr 2009, at 06:33, khalid hassan wrote:

Dear alps team

  I am using fulldiag program for a system of 2 by 2 plaquette  

on fermion hubbard. Now I want it to solve for 3 particles and Sz = 0.5. When I display the values for Sz, it comes out to be 1.5. By hit and trial I come to know that alps only calculating Sz=0.5 for one particle only, when there are three particles Sz comes out to be 1.5. I definitely making some mistake in input file.

I need a program that calculate

2 by 2 plaquette with fermion hubbard model with 3 particle and total spin 0.5

My program statements are as under but they are calculating 3 particles and total spin Sz= 1.5 which I even not mentioned.

LATTICE_LIBRARY="/temp/ALPS/xml/lattices.xml"; MODEL_LIBRARY="/temp/ALPS/xml/models.xml";

MODEL="fermion Hubbard"; LATTICE="anisotropic square lattice";

MEASURE_AVERAGE[Density]="n" MEASURE_AVERAGE[Magnetization]="Sz"

L=2; W=2;

U=10.0;

CONSERVED_QUANTUMNUMBERS="Sz,N";

Sz_total=0.5; N_Total=3;

{ t=1.0;}

I am student and therefore something I make comments in hurry.

Best Regards Khalid Loane