In this thesis the covariant Bethe-Salpeter equation formalism is usedto study some properties of ground-state baryons. This formalism relieson the knowledge of the interaction kernel among quarks and of the fullquark propagator. For the interaction kernel, which is in principle a sumof in?nitely many diagrams, I use the Ladder truncation. It amounts toreduce the interaction to a ?avor-blind quark-mass independent vector-vector interaction between two quarks, mediated by a dressed gluon. Theirreducible three-body interactions are neglected. The full quark prop-agator is obtained as a solution of the quark Dyson-Schwinger equationwhich is truncated such that, together with the truncation in the interac-tion kernel, chiral symmetry is correctly implemented. It is called Rainbowtruncation, and together with the truncated kernel equation it constitutesthe Rainbow-Ladder truncation of the Bethe-Salpeter equation.Any truncation induces the introduction of a model to account for theproperties of the full system. The main goal of this thesis is to evalu-ate the model dependence of corrsponding results and, as a consequence,to isolate the features related to the truncation itself. To this end twonon-related models are used to calculate the baryon spectra, from lightto heavy quarks, and the electromagnetic properties of the Delta(1232).From these results one concludes a qualitative model independence, andthat a Rainbow-Ladder truncated bound-state calculation reproduces thephysical results with an accuracy of 10%.Covariant bound-state equations are not limited to the study of hadronicbound states. As an example, in a further chapter of this thesis a Bethe-Salpeter equation for glueballs is proposed, and the main steps for a con-sistent resolution of the equation are described. However, to obtain thissolution is beyond the scope of this work. |