[Maximally helcitiy violating amplitudes](https://en.wikipedia.org/wiki/MHV_amplitudes): Amplituder med $n$ masseløse ekterne gaugebosoner, hvor $n-2$ har samme helisitet, og de to andre har den motsatte. Ved tree level så bryter disse helisitet maksimalt. (Amplituder hvor ett eller ingen av de eksterne gaugebosonene har motsatt helisitet summerer til $0$ (igjen at tree level).) Tree-level amplituder kan regnes ut svært effektivt via [[Parke-Taylor-formelen]]. Hva med loop level? [Trnka](https://youtu.be/rcGVL_S3Hwc?si=e6wi2dyktmyR6TER&t=2502): > This is just tree level. So then, the [progress started at 1 loop in the early 1990's](https://www.sciencedirect.com/science/article/abs/pii/0550321394901791) by [Zvi Bern](https://en.wikipedia.org/wiki/Zvi_Bern) and [Lance Dixon](https://en.wikipedia.org/wiki/Lance_J._Dixon) and [David Kosower](https://physics.aps.org/authors/david_a_kosower) when they used some improvement of these methods, called unitarity methods.