Ações efetivas para teorias de Gauge: campo eletromagnético e o campo de Kalb-Ramond

Abstract

The present dissertation presents the calculation of effective 1-loop actions for gauge theories such as the electromagnetic field and the Kalb-Ramond field. Effective actions work as quantum corrections to classical theories in order to explain certain quantum phenomena. For example, in electromagnetism, the nonlinear effects as the singularity of the self-energy of a point charge and the polarization of the vacuum. On the polarization of the vacuum the Euler-Heisenberg Lagrangian is highlighted. Thus, this work will present a method of calculation of the same denominated method of proper time, proposed by Schwinger. The analysis will follow the formalism of Path Integrals, thus allowing a very clear discussion. An analysis of the creation of electron-positron pairs in vacuum due to an external electromagnetic field will also be made. As well as, some applications of effective actions, such as the Casimir effect and the effective action at the finite temperature. In addition, the effective action for three-dimensional QED will also be calculated. And last the effective action for the Kalb-Ramond field will be calculated.