2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/68055Complexified spacetime algebra is defined as the geometric (Clifford) algebra of spacetime with complex coefficients, isomorphic $\mathcal{G}_{1,4}$. By resorting to matrix representation by means of Dirac-Pauli gamma matrices, the paper demonstrates isomorphism between subgroups of CSTA and SU(3). It is shown that the symmetry group of those subgroups is indeed $U(1) \otimes SU(2) \otimes SU(3)$ and that there are 4 distinct copies of this group within CSTA.8 pages, revised and extended compared to V.1General Mathematics15A66 (primary) 15A57; 16W30 (secondary)text