The gluon self-energy in cavity quantum chromodynamics

Bibliography: p. 78-79.A numerical technique to regularize divergent loop diagrams in cavity quantum chromodynamics is discussed, which is closely related to free space dimensional regularization. In this cavity regularization method, the energy shift is expressed as the integral of a divergent spectral function, from which the divergence may be extracted by analogy to the free space expression. It is shown for the case of the self-energy of a gluon in a cavity that no new divergences arise due to the presence of the boundary, provided that the regularization can be achieved in such a way that no subtractions are necessary. In order to avoid such subtractions, the so-called method of separation is developed, in which the spectral forms in the cavity are separated in such a way that the divergences of the various terms cancel exactly. This method is in close analogy to the free space regularization method of separation where tadpole contributions are separated off from the rest of the momentum integrals. The technique is used to evaluate the self-energy of a gluon in a cavity, which turns out to be positive for both the quark loop and the gauge loops. The positive value obtained offers a possible explanation for the absence of gluonic exotic states