I'm not sure about only measuring those two correlations (you might have to change the code for that), but, as to your last question, you should be able to use Sx:Sx because the Sx operator is defined in the models.xml file in terms of the raising and lowering operators. If you want to measure Sy, you would have to add the following lines to the models.xml file:
<SITEOPERATOR name="Sy" site="x"> 1/2*(Splus(x)-Sminus(x)) </SITEOPERATOR>
because it hasn't been defined as far as I can tell.
Good luck, Justin ________________________________________ From: comp-phys-alps-users-bounces@phys.ethz.ch [comp-phys-alps-users-bounces@phys.ethz.ch] On Behalf Of zhian asadzadeh [zhian.asadzadeh@gmail.com] Sent: Sunday, April 26, 2009 1:54 AM To: Comp-phys-alps-users@phys.ethz.ch Subject: [ALPS-users] Advanced correlation functions
Hi All,
I am using DMRG for my problem and I am going to measure diagonal and offdiagonal correlation functions. I am interest to obtain the correlation of first site with other sites and the middle site with other sites too. The output of DMRG consist of all the combinations which are possible but I just want the two correlations mentioned above because the output will be very large ( I am studying the ferrimagnetic chain with 100 sites). can I do that? how? And also can I use Sx:Sx for measuring off diagonal correlation functions?
Thanks, Zhian.