Supervisor: Steen Hannestad

Renormalization is a key concept in quantum field theory (QFT) and is used to handle infinities that arise in perturbative calculations of quantum interaction. This process allows physicists to absorb divergent terms into parameters such as electric charge and mass to obtain finite and meaningful results.  
In this colloquium, we explore the role of renormalization in Quantum Electrodynamics (QED) and Quantum Chromodynamics (QCD), with a focus on how the fine structure constant depends on the energies and how this changes our understanding of electromagnetic interaction.
We will conclude by discussing grand unified theories (GUT), which propose the unification of the strong, electromagnetic, and weak forces. GUT and QFT hypothesize that these three forces are unified at around 10^16 GeV, and it is believed that all four fundamental forces are interconnected.