Discrete charge, parity, and time symmetries (C, P, and T) of quantized fermion states are extended by a triality symmetry (t), producing the CPTt Group, transforming between three generations of fermions.
Cite
@article{arxiv.2407.02497,
title = {C, P, T, and Triality},
author = {A. Garrett Lisi},
journal= {arXiv preprint arXiv:2407.02497},
year = {2024}
}