Anomaly-free chiral fermion sets and gauge coupling unification

In this work we search for minimal sets of chiral fermions, with arbitrary quantum numbers, beyond the Standard Model that are anomaly-free and lead to vector-like particles
under SU(3) and U(1)_em after symmetry breaking. We further study which of these anomaly free
sets lead to unification of the gauge couplings at energy scales higher that 5.0×10^15 GeV in
order to be consistent with proton decay bounds. A similar study is performed in the context of
the SU(5) gauge group; for some of the anomaly-free sets found it is possible to obtain unification
of the gauge couplings with the extra fermions decoupling at high intermediate scales.