Hi,

Thank you so much for the help. That also worked. I was wondering if there was any method to measure four point correlation function (like <c_i^\dagger c_j c_k^\dagger c_l> for i,j,k,l all running over the lattice). I tried using fermion_hop as the two operators in MEASURE_CORRELATIONS but that didnt work. Could you please help me with this problem?

On Sun, Nov 30, 2014 at 10:26 PM, Matthias Troyer <troyer@phys.ethz.ch> wrote:
Alternatively you can also define Nup_total and Ndown_total in the standard Hubbard model/

On 30 Nov 2014, at 14:28, Sriluckshmy Viswanathan <sriluckus@gmail.com> wrote:

Hi Michele,

Wow. That worked. Thank you so much.

On Sun, Nov 30, 2014 at 6:46 PM, Michele Dolfi <dolfim@phys.ethz.ch> wrote:
Dear Sriluckshmy,


The model "fermion Hubbard” only knows about Nup and Ndown quantum numbers.
To conserve the total number of particles you should use the “alternative fermion Hubbard” model.


Best regards,
Michele

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Michele Dolfi
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dolfim@phys.ethz.ch
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> On 30 Nov 2014, at 12:24, Sriluckshmy Viswanathan <sriluckus@gmail.com> wrote:
>
> Dear all,
>
> I am trying to solve the fermion hubbard model on a square lattice with a small cluster size of 2x2 using exact diagonalization. I want to look at the energy levels at half filling. I used to N_total parameter to fix the filling, but the energy levels results dont change if I change this parameter. Could you please help me with this problem? I have attached the param file that I used. I am using fulldiag of ALPS.
>
> Regards
> Sriluckshmy
> <ferm_hubbard>




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Regards
Sriluckshmy




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Regards
Sriluckshmy