On the other hand, solutions to this equation for large initial values formula_4 cause the "rhs" to quickly approach zero as we descend in energy scale which locks formula_4 to the QCD coupling formula_2. This is known as a (infrared) quasi-fixed point of the renormalization group equation for the Yukawa coupling. No matter what the initial starting value of the coupling is, if it is sufficiently large it will reach this quasi-fixed point value, and the corresponding quark mass is predicted.