Abstract
Contents 4AbstractFor a long time, physicists dream of ”ultimate theory” which unifies all kindsof interactions in nature. The past years, countless experiments confirm theelementary particle interactions which are described by SU(3) × SU(2) × U(1) gauge theory so-called ”Standard Model” (SM) nowadays. Even sothe successes of SM, people run for the beauty of gauge theory with singlegroup which includes SU(3) × SU(2) × U(1) as the unified theory i.e. E6,SU(5), SO(10),...... . In this thesis, we study the general group structureand through the way also the applications in physics associates with it. Weinvestigate the exceptional group G2 unification theory, it turns out that it isdifficult to get the SM spectrum, even so we still get many interesting results.