Fayet-Iliopoulos term

A Fayet-Iliopoulos (FI) term is a concept from theoretical physics, specifically in supersymmetry, which introduces a constant parameter associated with a symmetry called U(1). Think of it as a background energy or charge added to a system, influencing how the fields (fundamental components of particles) behave and break symmetries spontaneously. This term can help explain how particles acquire mass and how certain forces in nature emerge, playing a role in constructing realistic models of particle physics beyond the Standard Model.