Renormalization Group Fixed Point with a Fourth Generation

In the Standard Model with four generations, at the two-loop level, we study the renormalization group equations for the Higgs quartic and Yukawa couplings and gauge couplings. The Yukawa sector is found to have a nontrivial fixed point structure. As the masses of the fourth family becomes sufficiently heavy, it will contain a natural scale $\Lambda_{FP} $ in the range of a few TeV to the order of $10^3$ TeV, above which the Higgs quartic and Yukawa couplings become practically constant. Around $\Lambda_{FP}$ the Yukawa couplings are strong and make it possible for the fourth generation to form bound states, including composite extra Higgs doublets.