• magnetic monopoles
• topological solitons
• General Relativity
• black holes
• Callan-Rubakov effect

This thesis deals with the topic of magnetic monopoles.
In the first chapter we begin by introducing the Dirac monopole, and then move on to
analyze in detail the ’t Hooft-Polyakov monopole solution in the SU(2) Yang-Mills-Higgs
theory.
In the second chapter we add gravity to the gauge theory studied in the previous
chapter, and perform a numerical study of the field equations. We investigate the essential
features of monopole-black hole transitions.
The third and final chapter is divided in two main sections: in the first one, we review
the Callan-Rubakov effect, meaning the possibility for monopoles to catalyze fermion
number violating processes; in the second section, we add gravity and study how the
Callan-Rubakov effect changes in curved spacetime.