= Ellis Ye Yuan
{c}
<Ellis Ye Yuan> co-developed the <scattering equations> with <Freddy Cachazo> and <Song He>, connecting massless-particle kinematics with marked points on a sphere.<Scattering Equations and KLT Orthogonality by Freddy Cachazo and others>[Definition and solution algorithm]{ref} In a common convention,
$$
\sum_{b\ne a}\frac{2k_a\cdot k_b}{\sigma_a-\sigma_b}=0,
$$
with conserved massless momenta $k_a$ and puncture coordinates $\sigma_a$. The equations provide algebraic structure for scattering calculations rather than trajectories of particles moving on that auxiliary sphere.
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