Yang–Mills theory
There is evidence that "N" = 4 supersymmetric Yang–Mills theory has an integrable structure in the planar large "N" limit. As the number of colors (also denoted "N") goes to infinity, the amplitudes scale like formula_16, so that only the genus 0 (planar graph) contribution survives. Planar Yang–Mills theory is a theory with a very large (infinite) number of colors.