# What if there were only 1 generation of fermions?

The number of fermion generations has many effects beyond the mere existence of "3 copies of fermions," including determining scatterings, constraining CP violation, influencing electroweak symmetry breaking, contributing to anomalous magnetic moments, and influencing baryogenesis.

How would the universe differ if there were only 1 generation of fermions, assuming no other standard model couplings changed? (Meaning the electron, 1-neutrino, up, & down Yukawa couplings; the CKM & PMNS phases; $$g_1$$, $$g_2$$, & $$g_3$$; the QCD vacuum angle; and the Higgs $$\lambda$$ & $$\mu$$ stay the same.)

Specifically, how would observed particle properties and interaction amplitudes change? And how would those changes affect baryon asymmetry and nucleosynthesis?

• This question (v3) seems too broad. – Qmechanic Sep 30 at 18:50
• Compared to this one? I based it on that, but I can narrow it if you like – alexchandel Sep 30 at 18:54
• If the question starts to get close votes, you might want to consider that. – Qmechanic Sep 30 at 19:05
• Narrowed it, better? – alexchandel Sep 30 at 19:59
• Obviously, 1×1 unitary matrix can have any phase $|\delta|=1$. – alexchandel Sep 30 at 21:51