<math>
\zeta = 2 \Delta \omega \, (R_2^A - R_2^B - p_A k_{\textrm{EX}} + p_B k_{\textrm{EX}}) = 2 \Delta \omega \, ( - p_A k_{\textrm{EX}} + p_B k_{\textrm{EX}}) \\
\Psi = (- p_A k_{\textrm{EX}} + p_B k_{\textrm{EX}})^2 - \Delta \omega^2 + 4 p_A p_B k_{\textrm{ex}}^2
= ( p_A k_{\textrm{EX}} + p_B k_{\textrm{EX}} )^2 - \Delta \omega^2 \\