anchor.diff:   !____________________________________________________________________________________
   
       do k = 1, n_cell
  -       file_length = 0
  +      file_length = 0
   
          r     = r_state%r(k)
          omega = x_state%Omega(k)
  
positive.code:     character(len = 8)                                     :: number_of_cell
      character(len = 64)                                    :: fname_tot
      integer                                                :: fid_tot
  
   ! For the critical points
      integer                                                :: index_fcp
      real(kind = x_precision)                               :: sigma_c_thick
  
negative.code:       write(number_of_cell,'(I5.5)') k
        fid_tot = 22 + k
        fname_tot = 's_curves/Temperature_Sigma_'//trim(number_of_cell)//'_tot.dat'
        
        open(fid_tot,file  = fname_tot, action='write',&
            status = 'replace', iostat = ios)
        if (ios /= 0) then
        write(*,*)"error while opening file", fname_tot
        stop
        endif
  
        write(fid_tot,'(3(A16))') 'Surface_density', 'Temperature', 'Optical_depth'
  
        do j = 1, nb_it
          temp_real(j)  =  temp_real(j) * state_0%T_0
  