
The gauge invariant generation of an effective gluon mass proceeds through the wellknown Schwinger mechanism, whose key dynamical ingredient is the nonperturbative formation of longitudinally coupled massless boundstate excitations. These excitations introduce poles in the vertices of the theory, in such a way as to maintain the SlavnovTaylor identities intact in the presence of massive gluon propagators. In the present work we first focus on the modifications induced to the nonperturbative threegluon vertex by the inclusion of massless twogluon boundstates into the kernels appearing in its skeletonexpansion. Certain general relations between the basic building blocks of these boundstates and the gluon mass are then obtained from the SlavnovTaylor identities and the SchwingerDyson equation governing the gluon propagator. The homogeneous BetheSalpeter equation determining the wavefunction of the aforementioned bound state is then derived, under certain simplifying assumptions. It is then shown, through a detailed analytical and numerical study, that this equation admits nontrivial solutions, indicating that the QCD dynamics support indeed the formation of such massless bound states. These solutions are subsequently used, in conjunction with the aforementioned relations, to determine the momentumdependence of the dynamical gluon mass. Finally, further possibilities and open questions are briefly discussed.
