I am using alps for the calculation of charge correlation function for the fermionic hubbard model. Now I want to calculate the current correlation function.

the expression for the charge correlation function is

< n_i : n_j > = < c_i^+ c_i : c_j^+ c_j >

the expression for the current correlation function is

< j_i : j_j > = < c_i^+ c_j : c_k^+ c_l >

Notice the changing indices in the current expression.

If it is possible then please give the program statements doing this

Best Regards

Khalid Loane