Electric charge quantization in 331 Models with exotic charges

The extensions of the Standard Model based on the $SU(3)_{C} \otimes SU(3)_{L} \otimes U(1)_{X}$ gauge group are known as 331 Models. Different properties such as the fermion assignment and the electric charges of the exotic spectrum, that defines a particular 331 model, are fixed by a $\beta$ parameter. In this article we study the electric charge quantization in two versions of the 331 models, set by the conditions $\beta=1/\left( 3\sqrt{3}\right)$ and $\beta=0$. In these frameworks, arise exotic particles, for instance, new leptons and gauge bosons with a fractional electric charge. Additionally, depending on the version, quarks with non-standard fractional electric charges or even neutral appear. Considering the definition of electric charge operator as a linear combination of the group generators that annihilates the vacuum, classical constraints from the invariance of the lagrangian, and gauge and mixed gauge-gravitational anomalies cancellation, the quantization of the electric charge can be verified in both versions.