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| Author(s): |
Clara Teixeira Figueiredo
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin |
| Defense date: | 2020-08-20 |
| Examining board members: |
Arlene Cristina Aguilar;
Adriano Antonio Natale;
Attilio Cucchieri;
Márcio José Menon;
Jun Takahashi
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| Advisor: | Arlene Cristina Aguilar |
| Abstract | |
In this work, we study the generation of a dynamical mass for the gluon in the nonperturbative region of QCD using the formalism of Schwinger-Dyson equations. We present a general analysis that preserves the transversality of the gluon self-energy, required from the non-Abelian gauge symmetry of the theory, and results in the infrared finiteness of the gluon propagator observed in several lattice simulations. This study is done within the Pinch Technique formalism, and its correspondence with the Background Field Method, and relies on the Ward identities satisfied by the nonperturbative vertices and a special identity named seagull identity. The result of these considerations is that the gluon can only acquire a dynamical mass when longitudinally coupled massless poles are incorporated into the vertices of the theory. These poles act as colored massless bound state excitations and can be studied under the context of Bethe-Salpeter equations. Previous works on the dynamics of such bound states considered only the possibility of a pole in the three-gluon vertex, neglecting effects from possible poles in the remaining vertices. Here, we study the impact that the ghost sector may have on the dynamical equation that describes the creation of such poles. This analysis reveals that the contribution of the pole associated with the ghost-gluon vertex is suppressed. We also study the gluon mass equation in the Landau gauge, taking into account its full nonlinear structure, contrary to what has been done in previous works, in which this equation was linearized by considering the gluon propagator as an external input. This eliminates the indeterminacy in the scale of the mass found in these previous analyses. In addition, our treatment of the multiplicative renormalization of the mass equation is carried out according to an approximate method inspired in several works about the quark gap equation. The resulting dynamical gluon mass is positive-defined and monotonically decreasing with the emerging gluon propagator matching rather accurately the data from large-volume lattice simulations (AU) | |
| FAPESP's process: | 16/11894-0 - Aspects of the dynamical mass generation in the formalism of the Schwinger-Dyson equations |
| Grantee: | Clara Teixeira Figueiredo |
| Support Opportunities: | Scholarships in Brazil - Doctorate |