Amplitude relations in heterotic string theory and Einstein-Yang-Mills

Understand

We present all-multiplicity evidence that the tree-level S-matrix of gluons and gravitons in heterotic string theory can be reduced to color-ordered single-trace amplitudes of the gauge multiplet.

• Explicit amplitude relations are derived for up to three gravitons, up to two color traces and an arbitrary number of gluons in each case.
• The results are valid to all orders in the inverse string tension $\alpha'$ and generalize to the ten-dimensional superamplitudes which preserve 16 supercharges.
• Their field-theory limit results in an alternative proof of the recently discovered relations between Einstein-Yang-Mills amplitudes and those of pure Yang-Mills theory.