# Notes on Biadjoint Amplitudes, ${\rm Trop}\,G(3,7)$ and $X(3,7)$ Scattering Equations

## TL;DR

This paper computes all biadjoint amplitudes for n=7, k=3 using tropical Grassmannians, and determines the exact number of solutions to scattering equations on X(3,7), revealing 1272 total solutions.

## Contribution

It introduces a novel method combining tropical geometry and explicit solutions to determine the total solutions for scattering equations at n=7, k=3.

## Key findings

- Number of solutions to scattering equations is 1272.
- Explicit solutions obtained are 1162 with high precision.
- The rank of the biadjoint amplitude matrix is 110.

## Abstract

In these notes we use the recently found relation between facets of tropical Grassmannians and generalizations of Feynman diagrams to compute all "biadjoint amplitudes" for $n=7$ and $k=3$. We also study scattering equations on $X(3,7)$, the configuration space of seven points on $\mathbb{CP}^2$. We prove that the number of solutions is $1272$ in a two-step process. In the first step we obtain $1162$ explicit solutions to high precision using near-soft kinematics. In the second step we compute the matrix of $360\times 360$ biadjoint amplitudes obtained by using the facets of ${\rm Trop}\, G(3,7)$, subtract the result from using the $1162$ solutions and compute the rank of the resulting matrix. The rank turns out to be $110$, which proves that the number of solutions in addition to the $1162$ explicit ones is exactly $110$.