Extended_zone_scheme

In the parameter file in the error name-space I suggest to add a variable for extended-zone scheme:

Number_of_BZ  =   2

If Number_of_BZ = 0 then we compute the trance for time displaced observables and S_(no,no_1) (q) for the equal time correlations. This is the very same as before.

If Number_of_BZ > 0 then the program will do the following for both the equal time and time displaced correlations:

S(q, tau)  =   \sum_{R}    e^{-i q (R + r_no1 +  r_no2)}  S_{no1,no2}(R) 

for q in

BZ   +  n b_1  + m b_2  

with n,m : 1... Number_of_BZ and

b_i a_j  = 2 \pi \delta_{i,j}