function s_tilde = get_s_tilde(pp,polarization)
include_globals
include_flags

t_matrix_tilde = inv(get_W(pp+1,pp,polarization))*get_W(pp,pp,polarization)*get_Phai(pp);
t_cell_tilde = mat2cell(t_matrix_tilde,[DIM,DIM],[DIM,DIM]);
t_tilde_11 = cell2mat(t_cell_tilde(1,1));
t_tilde_12 = cell2mat(t_cell_tilde(1,2));
t_tilde_21 = cell2mat(t_cell_tilde(2,1));
t_tilde_22 = cell2mat(t_cell_tilde(2,2));
t_tilde_22_inverse = inv(t_tilde_22);

tuu_tilde = t_tilde_11 - t_tilde_12*t_tilde_22_inverse*t_tilde_21;
rud_tilde = t_tilde_12*t_tilde_22_inverse;
rdu_tilde = -t_tilde_22_inverse*t_tilde_21;
tdd_tilde = t_tilde_22_inverse;

s_tilde = {tuu_tilde,rud_tilde;rdu_tilde,tdd_tilde};
end