To calculate this you will have to write your own worm code that creates two pairs of annihilation and creation operators (worms), since a single pair only gives you the Green's function.

Matthias

On Nov 19, 2012, at 5:23 PM, Michał Maik michal.maik@uj.edu.pl wrote:

Hi,

I was wondering if there was a way to calculate any 4 point correlation functions. I am interested in calculating:

<a_dag(i) a_dag(i) a(j) a(j)>

I would like to look at pair superfliudity and these correlation functions would be very useful.

As a side question, is there a way to use the winding numbers from the worms code output to study this effect? Thank you.

Best

Michal Maik