Collinear structure of amplitudes with massless particles

I will introduce the CHY formalism and show a way to treat collinear limits with it. I will show how to calculate the subleading order of the adjacent collinear gluon limit in pure Yang-Mills theory (YM) and argue why the result is interesting, including a novel formula connecting pure YM n-point amplitudes with two collinear gluons and pure YM (n-1)-point amplitudes with no collinear gluons.