On the other hand, solutions to this equation for large initial values typical for the top quark y t cause the expression on the right side to quickly approach zero as we descend in energy scale, which stops y t from changing and locks it to the QCD coupling g 3 . 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 at high energies to begin with, it will reach this quasi-fixed point value, and the corresponding quark mass is predicted to be about m ≈ ≈ 220 G e V .