The S Matrix of 6D Super Yang-Mills and Maximal Supergravity from Rational Maps

• Main Authors: Cachazo, Freddy, Guevara, Alfredo, Heydeman, Matthew, Mizera, Sebastian, Schwarz, John H, Wen, Congkao
• Format: Journal Article
• Language: English
• Published: 02-10-2018
• Subjects: Physics - High Energy Physics - Theory
• DOI: 10.48550/arxiv.1805.11111

We present new formulas for $n$-particle tree-level scattering amplitudes of
six-dimensional $\mathcal{N}=(1,1)$ super Yang-Mills (SYM) and
$\mathcal{N}=(2,2)$ supergravity (SUGRA). They are written as integrals over
the moduli space of certain rational maps localized on the $(n-3)!$ solutions
of the scattering equations. Due to the properties of spinor-helicity variables
in six dimensions, the even-$n$ and odd-$n$ formulas are quite different and
have to be treated separately. We first propose a manifestly supersymmetric
expression for the even-$n$ amplitudes of $\mathcal{N}=(1,1)$ SYM theory and
perform various consistency checks. By considering soft-gluon limits of the
even-$n$ amplitudes, we deduce the form of the rational maps and the integrand
for $n$ odd. The odd-$n$ formulas obtained in this way have a new redundancy
that is intertwined with the usual $\text{SL}(2, \mathbb{C})$ invariance on the
Riemann sphere. We also propose an alternative form of the formulas, analogous
to the Witten-RSV formulation, and explore its relationship with the symplectic
(or Lagrangian) Grassmannian. Since the amplitudes are formulated in a way that
manifests double-copy properties, formulas for the six-dimensional
$\mathcal{N}=(2,2)$ SUGRA amplitudes follow. These six-dimensional results
allow us to deduce new formulas for five-dimensional SYM and SUGRA amplitudes,
as well as massive amplitudes of four-dimensional $\mathcal{N}=4$ SYM on the
Coulomb branch.