CMSA Colloquium: Geometric Simplicity in Quantum Field Theory and Gravity

In physics we attribute much value to the emergence of simplicity, both conceptually and for computations. Familiar examples include algebraic relations among Feynman amplitudes, the surprising descriptions arising in large-N or duality limits, and the central role played by symmetries. In this colloquium we discuss how tame geometry allows one to quantitatively describe such simplifications by introducing a measure of complexity. This framework relies on finiteness: the information content of the functions and domains required to specify a theory, or an observable is finite. A key strength of the proposal is its generality as it applies to any physical quantity and can therefore be used both to analyze complexities within an individual Quantum Field Theory and to study the entire space of such theories. We present several applications and explain how this perspective ties in with our understanding of the expected properties of effective theories that can be coupled to Quantum Gravity.