Light-Shell Theory Foundations

We study the motivation and groundwork for the construction of a Light-Shell Effective Theory, an effective field theory for describing the matter emerging from high-energy collisions and the accompanying radiation. We begin in chapter 2 with a simple electrodynamics calculation to motivate the picture of the ``light-shell," in which all electric and magnetic fields lie on a spherical shell that moves outward at the speed of light. The result turns out to do more than motivate, as it also hints at an important feature of the theory, namely the gauge in which we subsequently choose to do calculations, called Light-Shell Gauge.