Multiplicity of particle families in the Standard Model

Determine the theoretical origin of the multiplicity of families (generations) of elementary particles in the Standard Model of particle physics by identifying principles or mechanisms that necessitate and explain the observed replication of fermion families.

Background

In discussing the role of symmetry principles in modern physics, the paper notes that although the Standard Model successfully accounts for a wide array of phenomena, it remains largely phenomenological. The authors emphasize that key structural features of the Standard Model are not yet derived from deeper principles.

Among the unresolved issues, the paper explicitly lists the multiplicity of families of elementary particles as an example of what remains unexplained, highlighting a foundational gap in understanding why multiple generations of fermions exist.

References

One should note, however, that the Standard Model provides only a phenomenological description of elementary particles—its symmetries and basis states were largely selected based on the enormous experimental work that engaged the entire global community over the course of over a century. Many aspects of this model (multiplicity of families of elementary particles, origin of particle charges, etc.) remain unexplained.

— Derivation of the Schrodinger equation from fundamental principles  (2603.27041 - Zhang et al., 27 Mar 2026) in Section 3, Conclusions and Prospects